Process for producing thermoplastics

ABSTRACT

A process for preparing thermoplastics or polymer blends comprising (A) from 5 to 95% of a water-moist elastomer component containing up to 60% of residual water, (B) from 5 to 95% of a thermoplastic polymer, (C) from 0 to 95% of a further polymer, and (D) from 0 to 70% of additives, said process comprising mixing the components A to D in an extruder with mechanical dewatering of component A, wherein the extruder has at least two rotating screws and, in the conveying direction, is essentially composed of a metering section into which component A is fed, a squeeze section which serves for dewatering component A and contains a retarding element and an associated dewatering orifice which is present upstream of the retarding element by a distance corresponding to at least one screw diameter, a feed section in which the thermoplastic polymer B is introduced as a melt into the extruder, a plastication section with mixing or kneading elements, a devolatilization section with an orifice and in which the remaining water is removed as steam, and a discharge zone.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a novel process for the preparation oftoughened thermoplastics or polymer blends containing toughenedthermoplastics, the thermoplastics or the polymer blends comprising

A) from 5 to 95% by weight of at least one water-moist elastomercomponent A containing up to 60% by weight of residual water,

B) from 5 to 95% by weight of at least one thermoplastic polymer B,

C) from 0 to 95% by weight of at least one further polymer C, and

d) from 0 to 70% by weight of additives D,

by mixing the elastomer component A with the thermoplastic polymer Band, if present, the further polymer C and, if present, the additives Din an extruder with mechanical dewatering of the elastomer component A.

The present invention furthermore relates to molding materials preparedby the process and the use of the molding materials for the productionof films, fibers and moldings. Finally, the present invention relates toan extruder for the preparation of the thermoplastics.

BACKGROUND OF THE INVENTION

Particulate rubbers which may be grafted or ungrafted are frequentlyused as elastomer components for toughening thermoplastics or otherplastics. Such rubbers are usually prepared in aqueous systems, forexample by emulsion or suspension polymerization. The particles formedin the suspension polymerization or precipitated in the emulsionpolymerization (for example by adding a coagulating precipitating agent)are as a rule washed with water and dewatered by a suitable dewateringmethod, such as sieving, pressing out, filtration, decanting, settlingout, centrifuging or partial thermal drying, for example by means of apneumatic dryer. Partial dewatering by spray drying is also possible.Partially dewatered products are obtained in every case.

DETAILED DESCRIPTION OF THE INVENTION

Frequently used graft rubbers are, for example, polybutadiene graftedwith a styrene/acrylonitrile copolymer (SAN) and poly-n-butyl acrylategrafted with such a copolymer, or rubbers composed of a plurality ofgraft stages and based on butadiene, styrene, n-butyl acrylate,ethylhexyl acrylate, methyl methacrylate and/or acrylonitrile.

The residual water content of the rubber obtained after partialdewatering is up to 60% by weight and is usually removed byenergy-intensive drying. The dried rubber obtained as a powder isfinally incorporated into the thermoplastics present as powder orgranules with melting, the end product being formed. Processes in whichrubber polymers and matrix polymers are precipitated and dried togetherare also known. Owing to the content of fine dust, the rubber powdertends to undergo spontaneous ignition during the drying and theincorporation into the thermoplastics.

According to a proposal described in DE-A-20 37 784, partially dewateredgraft rubber can be mixed into an SAN melt under superatmosphericpressure and a thermoplastic containing this graft rubber can beobtained with evaporation of the water. This process requires arelatively large amount of electrical energy.

EP-A 534 235 describes a process for the preparation of toughenedthermoplastics by incorporating rubber subjected to partial mechanicaldewatering into a thermoplastic above the softening point of thethermoplastic, the incorporation being effected in a main extruder andthe partial dewatering of the rubber being carried out in a sideextruder mounted at the side of the main extruder. The residual waterremaining in the rubber is removed as steam during the incorporation,through devolatilization orifices present before and after the feedpoint. The disadvantage of this process is the necessity of operatingtwo extruders for the preparation of the impact-resistant thermoplastic.

The German utility model DE-U 94 21 779 discloses an extruder forcompounding moist material in which washed plastic wastes are pushedinto the extruder using a stuffing device (stuffing screw). The wateradhering to the chopped plastic pieces is removed through an opening inthe extruder, the opening being provided with a screw to retain theplastic.

U.S. Pat. No. 5,151,026 describes an extruder in which comminuted andwashed plastics wastes whose water content is up to 50% by weight aredewatered. For this purpose, short sections having a left-handed threadare present in the extruder screw, which otherwise has a right-handedthread in the usual manner. A devolatilization orifice is present in theregion of the left-handed thread sections or immediately before theleft-handed threads. The extruder content is under high pressure(pressure maximum) in this region owing to the retarding effect of theleft-handed threads, and the devolatilization orifice must therefore beclosed by means of an extruder which prevents the polymer from emerging.This technically complicated seal is disadvantageous. The divisionalapplication U.S. Pat. No. 5,232,649 based on this U.S. patent describesthe corresponding process.

EP-A 233 371 discloses a process for the preparation of a thermoplasticresin, in which the latex of a graft rubber, a water-solubleprecipitating agent and an organic solvent are mixed to give a two-phasemixture and the aqueous phase is separated off. The organic phase isdevolatilized in an extruder, mixed with the metered melt of astyrene/acrylonitrile copolymer and devolatilized again and the productis discharged. The disadvantages of these expensive processes is thatlarge amounts of water initially have to be used and then removed again,that expensive and rapidly evaporating organic solvents must be handledand that graft rubber particles are increasingly entrained by theoutflowing gas during devolatilization before the addition of the SANmelt.

JP 01 123 853 discloses a process in which the latex of a graft rubber,a water-soluble precipitating agent and an organic chemical are mixed ina kneader, the latex being coagulated. The coagulated latex is separatedoff in the kneader and is further dewatered and devolatilized in anextruder. The process has the disadvantages that large amounts of liquidhave to be handled, with the result that the throughput (amount ofproduct per unit time) is low, that the latex coagulation is part of theprocess and takes place in a technically complex kneader (instead of,for example, in a simple stirred container), and that the solution ofthe precipitating agent may cause corrosion in the kneader.

JP 22 86 208 describes a twin-screw extruder for dewateringthermoplastic molding materials, whose screws having a right-handedthread each possess two left-handed thread sections. The water passes inliquid form through Seiher housings--sieve-like inserts in the extruderbarrel--and emerges as steam through devolatilization orifices. However,the Seiher housings tend to become blocked by emerging polymer material,as described, for example, in DE 15 79 106 for the dewatering ofsynthetic rubber. The preparation of the molding materials is thussusceptible to problems. The extruder must be stopped in order to cleanthe Seiher housings blocked by outgoing polymer, and the Seiher housingsthen have to be disassembled, cleaned and reassembled. These downtimesmake processes using Seiher housings uneconomic (short operating times).

JP-A 1/202 406 likewise describes a process in which moist rubber-likepolymers are first partially dewatered in an extruder, in a regionprovided with Seiher housings, and the remaining water is then removedin one atmospheric and three downstream reduced-pressuredevolatilization zones. In addition to the disadvantageous, susceptibleSeiher housings, this process also includes an expensivereduced-pressure devolatilization region.

JP-A 57 16 7303 describes a process in which polymer particles areseparated off from their aqueous suspension (slurry) by filtration andare further dewatered in an extruder, the water emerging through Seiherhousings. The extruder content is then heated up, melted under pressure,devolatilized twice, mixed with additives and discharged. The maindisadvantage of this process is the use of the Seiher housings in theextruder, which readily become blocked, resulting in short operatingtimes.

JP 4008 754 describes a process for the preparation of a thermoplasticresin, in which the latex of a diene graft rubber is dewatered in atwin-screw extruder, the water emerging through Seiher housings. Theextruder content is then devolatilized and melted, after which a melt ofa vinyl polymer is fed to the extruder. This process, too, requires theuse of the problematic Seiher housings.

U.S. Pat. No. 4,802,769 describes an extruder in which a slurry of arubber polymer is processed together with a styrene/acrylonitrilecopolymer to give a thermoplastic. The water passes in liquid formthrough Seiher housings and emerges as steam through a three-stagedevolatilization process. In addition to the Seiher housings whichbecome blocked, the disadvantages are that the extruder part providedwith Seiher housings is heated and that a multiple pressure build-up dueto retarding elements occurs in the devolatilization part, with theresult that the polymer material is subjected to high thermal andmechanical stress.

It is an object of the present invention to provide a process which doesnot have the disadvantages described. In particular, it is intended toprovide a process which permits the preparation of an impact-resistantthermoplastic comprising at least one water-moist elastomer componentand one or more thermoplastic, brittle polymers in a technically simplemanner, as far as possible in one process step.

It is a further object of the present invention to provide a process bymeans of which polymer blends can be prepared in one process step bymixing of the thermoplastic with further polymers. In particular, aprocess should be provided which has the flexibility to permit theblending of even the most different polymers with one another and alsothe blending of greatly varying quantity mixing ratios of thermoplasticpolymer and elastomer component (giving toughened thermoplastics havingthe low to very high rubber contents) and which at the same time isreliable in operation.

Furthermore, the process should enable the thermoplastic or the polymerblend to be mixed with conventional additives (for example, stabilizers,dyes, fillers, etc.) without additional process steps, it also beingpossible to introduce the additives in the form of masterbatches.

The process should furthermore subject the polymer material to verylittle thermal and mechanical stress.

Finally, the process should have a high throughput and ensure a longeroperating time without problems. In particular, it should be ensuredthat the residual water can be removed in a trouble-free manner evenover a relatively long operating time of the process.

We have found that these objects are achieved by the process defined atthe outset, wherein the components A, B, C and D are fed to an extruderwhich has at least two screws rotating in the same direction or inopposite directions and having a screw diameter D_(Screw), and, in theconveying direction (downstream), the extruder being essentiallycomposed of

at least one metering section in which elastomer component A is fed tothe extruder by a metering means,

at least one squeeze section which serves for dewatering the elastomercomponent A and contains at least one retarding element and in each caseat least one associated dewatering orifice which is upstream of the(first) retarding element by a distance corresponding to at least onescrew diameter D_(Screw),

at least one feed section in which the thermoplastic polymer B isintroduced as a melt into the extruder,

at least one plastication section provided with mixing and/or kneadingelements,

at least one devolatilization section which is provided with at leastone devolatilization orifice and in which the remaining water is removedas steam, and

a discharge zone,

wherein some or all of the water emerging from the dewatering orificesis present in the liquid phase, and

wherein the components C and/or D are fed to one or more of the statedextruder sections together or separately from one another, eithertogether with the components A and/or B or separately from A and B.

We have also found the thermoplastic molding materials prepared by theprocesses, and the use of these molding materials for the production offilms, fibers and moldings. Finally, we have found an extruder for thepreparation of the thermoplastics.

The principle of the process and the preferred embodiments of theprocess are described below, those components of the extruder which arereferred to as sections or zones not necessarily being identical to theindividual components, such as barrel parts and screw segments, fromwhich the extruder is assembled. A section or a zone consists as a ruleof a plurality of components. The numbers stated in connection with thesections or zones refer to FIG. 1, which schematically shows one of thepossible embodiments of the extruder.

In a preferred embodiment, the extruder is a twin-screw extruder.However, it is also possible to use an extruder having three or morescrews or an extruder having a main screw of large diameter and,arranged around this, small screws (planetary arrangement).

The screws of the extruder, furthermore, preferably rotate in the samedirection. However, rotation in opposite directions is also possible.Particular preference is given to a twin-screw extruder having screwsrotating in the same direction.

The water-moist elastomer component A containing up to 60% by weight ofresidual water is, as a rule, a moist solid. It is, for example, a graftrubber which was obtained by emulsion polymerization, precipitated andpartially dewatered to a residual water content of up to 60% by weight,where the partial dewatering may be effected, for example, byfiltration, settling out, pressing out, decanting, centrifuging orthermal drying. The elastomer content A containing residual water is fedto metering section 2 of the extruder. The metering section usuallyconsists of an automatic metering means and the actual metering orifice(or a plurality of metering orifices). The metering means is in the formof, for example, a conveying screw which conveys or forces the conveyedmaterial into the metering orifice. It is also possible for component Ato be metered by suitable gravimetric or volumetric metering means andto be metered under gravity into the feed orifice of the extruder. Thecomponent A is drawn in and vented by means of a suitable screw geometryin the metering section.

If there are a number of elastomer components A, these may be meteredtogether or separately from one another into the same metering orificeor into different metering orifices of the metering section 2.

In a possible embodiment, a vent section 1 is located upstream in thedirection opposite the conveying direction of the extruder. Typically,it has one or more vent orifices through which occluded air in theelastomer component can escape.

In a further embodiment, the component C and/or the component D orproportions of the total added amount of components C and/or D aremetered into the vent orifice or into one or more further orificesarranged in the vent section. If both components C and D are fed in,this may be done by feeding said components together through one orificeor through different orifices (one each for C and D).

In another, preferred embodiment, the component C and/or the component Dor proportions of the total added amount of components C and/or D aremetered into the metering orifice of the metering section or into one ormore further orifices arranged in the metering section. This may also beeffected in a further metering section 2' which is downstream of thefirst metering section 2 and for which essentially the statements madein connection with section 2 are applicable.

Components C and D can be fed into the metering sections of theextruder, separately from A or together with A in one of the followingcombinations: A+C+D, A/C+D, A+C/D, A+D/C and A/C/D (where / meansseparately from, each by means of a separate orifice, and + meanstogether with, through a common orifice).

In both stated embodiments, the metering means for the components Cand/or D may be, for example, a conveying screw as in the case of themetering of the elastomer component A, a pump or an extruder, dependingon the state of aggregation of C and D.

In the region of the metering sections and--if present--in the ventsection, the extruder screws are formed, as a rule, as conventionalconveying screws. For the purposes of this application, conventionalconveying screws are, for example, elements having an earth mixerprofile (completely self-purging), elements having a thrust edge,elements having a trapezoidal profile and elements having a rectangularprofile, screw elements having conveying threads of large pitch (pitchlarger than the diameter of the screw) in the conveying direction(termed RGS elements) or combinations of these elements, it also beingpossible for the screws to be equipped with a smaller or larger numberof flights compared with the squeeze section. Double-flight andsingle-flight screw elements may also be used together here. The screwelements of the conveying screw may be identical or different in thestated sections; furthermore, they can have identical or differentpitches.

The water-moist elastomer component is conveyed downstream into thefirst squeeze section.

In the first squeeze section 3, a part of the residual water containedin the elastomer component is mechanically removed (squeezing). Thematerial is conveyed against a retarding element which acts as anobstacle and is present, as a rule, at the end of the squeeze section.This builds up a pressure, which forces water out of the elastomercomponent. The pressure can be built up by different arrangements ofscrew elements, kneading elements or other retarding elements, dependingon the Theological behavior of the rubber. In principle, all commercialelements in the apparatus serving for building up the pressure aresuitable.

Examples of possible retarding elements are

pushed-over, conveying screw elements

screw elements having a pitch opposite to the conveying direction,including screw elements having conveying threads of large pitch (pitchlarger than the diameter of the screw) opposite to the conveyingdirection (termed LGS elements)

kneading blocks having nonconveying kneading disks of different width

kneading blocks having a back-conveying pitch

kneading blocks having a conveying pitch

barrel disks, eccentric disks and blocks configured therefrom

toothed mixing elements of various design

neutral retarding disks (baffles)

mechanically adjustable restrictors (sliding barrel, radial restrictors,central restrictors).

Two or more of the retarding elements may be combined with one another.The retarding effect can also be adapted to the respective elastomer bymeans of the length and the intensity of the individual retardingelements.

In the squeeze section, the screw elements situated before therestricted flow zone (before the first retarding element) are generallyconstructed as conventional conveying screws. In an embodiment, theconveying screws used here have a helix angle which becomes shallowertoward the restricted flow zone. This construction brings about arelatively slow rise in pressure, the term transition zone beingfrequently used, which can be advantageous for dewatering certainelastomer components.

In another preferred embodiment, the increase in pressure occurs withouta prior transition zone (ie. the conveying screw generally has aconstant pitch in the squeeze section), and therefore occurs immediatelybefore or in the restricted flow zone.

In another preferred embodiment, mixing elements and/or kneadingelements, examples of which are given below for the plastication section5, are used in the squeeze section between the dewatering orifice andthe first retarding element. This embodiment can be advantageous inparticular for certain consistencies and morphologies of the elastomercomponent.

In the first squeeze section, all structural features and all operatingparameters of the extruder are preferably tailored to one another insuch a way that, at the chosen screw speed, the elastomer material isconveyed and compressed but is plasticated or partly melted only to aminor extent, if at all, and is not completely melted.

The squeeze section 3 of the extruder preferably contains, for apressure build-up, screw elements having a pitch opposite to theconveying direction and/or corresponding kneading blocks.

The water forced out of the elastomer material in the first squeezesection leaves the extruder in the liquid phase and not as steam. In aless preferred embodiment, up to 20% by weight of the water removed inthis section emerge as steam.

The squeeze section is provided with one or more dewatering orifices.The dewatering orifices are preferably located at the top of theextruder; however, lateral or downward pointing arrangements arepossible. Furthermore, dewatering orifices are preferably provided withan apparatus which prevents the emergence of the conveyed elastomer A.Retaining screws are particularly preferably used for this purpose.

The dewatering orifices are designed in a manner known per se and theirgeometry substantially corresponds to the known devolatilizationorifices, as used for removing gaseous substances from an extruder. Thedewatering orifices used are ones whose shape and dimensions are chosenso that the orifices cannot be blocked by the extruder content. Cut-outsand/or holes in the extruder barrel are particularly preferably used asdewatering orifices. Examples of suitable dewatering orifices arecircular holes or holes with the shape of a figure 8 lying on its side(ie. two circular holes directly adjacent to one another), where thelongitudinal axis of the figure 8 may, for example, be arranged at aright angle (perpendicular) to, or parallel to (along), the conveyingdirection of the extruder. The dewatering orifice may moreover bepositioned centrally on the longitudinal axis of the extruder (ie.symmetrically) or to one side of the longitudinal axis of the extruder(ie. asymmetrically).

In a preferred embodiment, the dewatering orifices used are not Seiherhousings, or similar components which readily become blocked, such asscreens. Seiher housings are, to be specific and as already described,susceptible to blockages.

According to the invention, the dewatering orifice belonging to theretarding elements is located before the retarding element or, in thecase of a plurality of retarding elements, before the first retardingelement upstream by a distance corresponding to at least one screwdiameter D_(Screw), preferably from 1 to 4 D_(Screw), very particularlypreferably from 1 to 3.5 D_(Screw). distance is to be understood as thedistance between the middle of the dewatering orifice and the beginningof the first retarding element.

As a result of this distance between retarding elements and dewateringorifice, the dewatering orifice is not present in that region of theextruder in which the pressure of the polymer conveyed against theretarding elements is very high (pressure maximum). Technically simpleapparatuses, such as retaining screws, are therefore sufficient forsealing the orifices to prevent polymer from emerging.

The temperature of the emerging water is in general from 20 to 95° C.,preferably from 25 to 70° C., measured at the outlet orifice.

In the first squeeze section, from 10 to 90, preferably from 20 to 80, %by weight of the initially contained residual water are usually removed,depending on the elastomer component and on the residual water contentinitially present.

To improve the dewatering performance of the first squeeze section, itcan be advantageous to use retarding elements and/or kneading elementsin the metering section or between the metering section and the firstdewatering orifice. The type and number of these retarding and/orkneading elements are selected so that the elastomer component issubjected to a degree of mechanical load, thus changing its nature sothat it becomes easier to dewater, but not, or only to a subordinateextent, plasticizing it or causing it to begin to melt, and certainlynot melting it completely.

In a preferred embodiment, the extruder is not heated in the meteringsections for the elastomer component A and in the squeeze sections. Inone embodiment, the extruder is cooled in these stated sections.

The partially dewatered elastomer component A is transported away viathe retarding zones and enters the next extruder section.

In an embodiment preferred for the preparation of some impact-resistantthermoplastics, the first squeeze section 3 just described is followedby a second squeeze section 3', which in turn consists of a conveyingsection and a retarding zone effective as an obstacle. The statementsmade in connection with the first squeeze section 3 are essentiallyapplicable to this section.

In the optional second squeeze section, the elastomer component isfurther dewatered, once again up to 80, preferably up to 65, % by weightof the water present initially (before the extrusion) being removed. Asa result of the mechanical energy introduced by the rotating extruderscrew, the temperature of the elastomer component in the second squeezesection generally increases to values up to 250° C.

The process is preferably designed so that the contents of the extruderare exposed to temperatures which are as low as possible. The extruderis therefore preferably designed and operated so that the temperature ofthe elastomer component does not exceed 200° C., particularly preferably180° C. These temperatures are based on the restricted flow zones.

From 20 to 99% by weight of the water removed in the second sectionemerges as liquid, and the remaining amount to 100% by weight as steam.However, the dewatering orifices are preferably designed so that theamount of water emerging in liquid form is 70% by weight or more, inspite of the high material temperature. For this purpose, the geometriesof extruder screws and of the retaining screws are designed in such away that the water remains predominantly in liquid form, for example asa result of a pressure build-up in the outlet zone or as a result ofother measures.

As a rule, the temperature of the water leaving the extruder is from 40to 130, preferably from 50 to 99° C.

The partially dewatered elastomer component can be melted to arelatively large extent or completely melted at the end of the secondsqueeze section 3' and can be present in the form of relatively largefused agglomerates.

The extruder may contain further squeeze sections behind the secondsqueeze section 3', particularly when the initial residual water contentof the elastomer component A is high.

The water which is squeezed out generally leaves the extruder throughall of the dewatering orifices which are present. Depending on theproperties of the elastomer component and on the amount which is meteredin (degree of filling of the extruder) and its residual water content,it is also possible, however, that the water which is squeezed out isnot discharged at all of the available dewatering orifices, and theother dewatering orifices can be described as dry, ie. no or virtuallyno water passes out therethrough. This has proven not to be at alldisadvantageous.

In a preferred embodiment, the water removed in the squeeze sections,including any elastomer particles which it may carry, can be collectedand, for example, used in the preparation of components A, B, C and/orD. Thus, the water which is squeezed out may, for example, be used againin the preparation of the elastomer component A or for precipitating therubber from its latex. This recycling of the water improves thecost-effectiveness and the environmental compatibility of the process,since there is less waste water.

After passing the last squeeze section, the elastomer component has beenfreed from a considerable part of the residual water (component A') andenters a feed section 4 in which one or more feed orifices for thethermoplastic polymer B are present. It is advantageous that the polymerB is introduced in the form of its melt. If the feed section contains aplurality of feed orifices, these may be arranged, for example, onebehind the other along an imaginary axis in the longitudinal directionof the extruder, in a circle along the extruder circumference or alongan imaginary helix around the extruder.

The melt of the polymer B can be fed in by means of an extruder or byconveying means, such as melt pumps or metering screws.

In the feed section 4 described, the component C and/or the component Dor proportions of the total added amount of the components C and/or Dmay be introduced into the extruder, in addition to the melt of athermoplastic polymer B. These components may be present as a melt orliquid and in this case are generally metered in by metering means asalso used for feeding the melt of the polymer B or, if the component isliquid, by means of a liquid pump. In the case of solid components Cand/or D, the metering is usually effected as described in the case ofcomponent A.

The components C and D can be fed to the extruder separately from B ortogether with B, in one of the following combinations: B+C+D, B/C+D,B+C/D, B+D/C and B/C/D (where / means separately from, each by means ofa separate orifice, and + means together with, through a commonorifice).

The components C and/or D or proportions of the total added amount ofthe components C and/or D, in unmelted or not completely melted form,may also be fed to section 4 or the above-described sections 1 and 2 ofthe extruder by means of a positive metering element. Such a meteringelement is, for example, an extruder, in particular a twin-screwextruder having intermeshing screws running in opposite directions.

The use of a melt pump, of an extruder (ie. side extruder) or of ametering pump as a metering means for the components C and/or D ispreferred.

In the region of feed section 4 in which the melt of the thermoplasticpolymer B and, if required, the components C and/or D are fed in, thescrew may, for example, be in the form of a conveying screw which iscapable of homogenizing the mixture of elastomer component A and themelt of thermoplastic B and, if required, components C and/or D only toa small extent. The statements made with regard to the metering sectionare applicable to the design of the conveying screw.

In a preferred embodiment, in addition to section 4 which is presentbetween the (last) squeeze section and the (first) plastication section5 (see below), the extruder has, at another point, further sections 4',4", etc. in which a melt of the thermoplastic polymer B is likewise fedin. In particular, these further feed sections 4', 4", etc. are locateddownstream in the region behind the feed section 4 and before the end ofthe extruder.

The feeding of the melt of B via a number of feed sections, 4, 4', 4",etc. can be advantageous in particular if specific product formulationsare desired. In a preferred embodiment, there are further feed sections4', 4", etc. for the melt of the thermoplastic polymer B downstreambetween the plastication and devolatilization sections, between twodevolatilization sections, between the last devolatilization section andthe discharge zone, or in the discharge zone. The last two of theseembodiment are preferred.

If the melt of B is fed to the extruder via a number of feed sections 4,4', 4", etc., the distribution of the total amount of B across thedifferent sections 4, 4', 4", etc. can vary within wide limits. In thecase of two feed sections 4 and 4', the weight ratio [melt of B insection 4/melt of B in section 4'] may be from 9.5:0.5 to 0.5:9.5,preferably from 9:1 to 1:9, and particularly preferably from 8.5:1.5 to1.5:8.5. The properties of the product of the process can be influencedto a certain extent by distributing the total amount of B across theindividual sections 4, 4', 4", etc.

The feed section for the thermoplastic melt B and, if required,components C and/or D is followed by a plastication section 5 which isprovided with mixing and/or kneading elements.

The mixing and/or kneading elements homogenize the polymer blend withsimultaneous melting of the dewatered elastomer component A' and, ifrequired, of the components C and/or D.

Suitable mixing and kneading elements are the components familiar to aperson skilled in the art, for example

screw elements having a small pitch in the conveying direction,

kneading blocks having narrow or broad, conveying or nonconveyingkneading disks,

screw elements having a pitch opposed to the conveying direction,

barrel disks, eccentric disks and blocks comprising these disks,

toothed mixing elements or

melt mixing elements

or a combination of such elements. It is also possible to use the screwelements given as examples for the retarding elements, since eachretarding element generally also has a mixing effect. Preference isgiven to the use of different combinations of kneading blocks as mixingand kneading elements for plastication. Baffles may also be used withadvantage. All of the abovementioned elements may be used in normaldesigns corresponding to the diameter of the extruder barrel or else asa specific design with reduced diameter.

Furthermore, all of the abovementioned elements may also be modified inanother manner, eg. to achieve gentle processing conditions for thecontents of the extruder, or more intensive mixing. Conveying threadsand/or kneading blocks may be provided with intermeshing elements havingapertures and/or reduced diameters.

The choice of the type, number and dimensions of the screw elements inthe plastication section depends on the components of the polymermixture, in particular on the viscosity and softening temperature andthe miscibility of the components.

The extruder may contain one or more further plastication sections 5'after the plastication section described, for example if thehomogenization and the melting of the blend was incomplete in the firstplastication section. The statements made in connection with the firstplastication section are correspondingly applicable to the furtherplastication section or sections.

It is possible to feed the component C and/or the component D orproportions of the total added amount of the components C and/or D to atleast one of the plastication sections, these components being fedseparately from one another through different orifices or togetherthrough a common orifice.

In a preferred embodiment, the melt of the thermoplastic polymer B and,if required, the components C and/or D are fed to the extruder at thebeginning of the plastication section. In this embodiment, the feedsection for the melt of the thermoplastic polymer B accordinglycoincides with the beginning of the plastication section 5.

In a further particular embodiment, the melt of the thermoplasticpolymer B and, if required, the components C and/or D are fed to theextruder at one or more points in the plastication section. In thisembodiment also, therefore, the feed section 4 coincides with theplastication section 5.

In a further particular embodiment of the extruder, one or more furtherplastication sections are present before feed section 4 in which themelt of the thermoplastic polymer is fed in, ie. behind the last squeezesection. In this plastication section 5", the very substantiallydewatered elastomer component A', for example the rubber powder, isfirst homogenized and plasticated alone. The melt of the thermoplasticpolymer B and, if required, the components C and/or D are accordinglyintroduced into a viscous melt of the elastomer component A' in thisembodiment. In this case, the plastication section 5 downstream of themixing of melt B and C and/or D (section 4) serves merely forhomogenizing the mixture of the components already present in theplastic state.

The choice of the variants described for feeding in melt B andoptionally the components C and/or D, ie.

into a conveying section before the plastication section,

at the beginning of the plastication section,

at one or more points in the plastication section,

into a conveying section between two plastication sections,

depends on the ratios and on the physical and chemical properties of thecomponents A, B, C and D to be mixed. The viscosities of the melts ofelastomer component A' and thermoplastic polymer B and (if metered intothis part of the extruder) of the components C and/or D, the softeningtemperatures of the components, their thermal load capacity or tendencyto decompose at relatively high temperatures, the compatibility in termsof miscibility or wettability of the components, the residual watercontent of the polymer blend comprising elastomer component A' andthermoplastic polymer B and, if required, the components C and D and, inthe case of particulate components, their particle size and particlesize distribution may be mentioned merely by way of example.

The last plastication section is followed by one or moredevolatilization sections 6 and/or 6', each of which is provided withone or more devolatilization orifices. In the devolatilization sections,the remaining residual water which was not mechanically removed in thesqueeze sections is partially or completely removed. Because thetemperatures of the polymer melt are usually above 100° C., the watergenerally emerges completely as steam. The energy required forevaporating the water has, as a rule, already been introduced into theplastication sections. However, it is also possible to supply the energyin a conventional manner by heating the extruder barrel.

The devolatilization orifices are preferably present at the top of theextruder. However, other arrangements are also possible, cf. thestatements made in connection with the position of the feed orifices forthe melt of the thermoplastic polymer B, which are also applicable incontext for the devolatilization orifices.

A lateral arrangement (on one side or both sides) of thedevolatilization orifices is likewise preferred, and particularpreference is given to a lateral arrangement in which all of the surfaceareas of the devolatilization orifice face downward, so that dischargedpolymer constituents and condensed steam cannot flow back into theextruder. Insofar as the properties of the extruder contents permitthis, the devolatilization orifices may also be situated on theunderside of the extruder. The devolatilization orifices are preferablyprovided with a connection piece.

The devolatilization orifices may be operated under atmospheric, reducedor superatmospheric pressure, and all devolatilization orifices may havethe same pressure or different pressures. In the case of reducedpressure, the absolute pressure is usually from 100 to 500 mbar; in thecase of devolatilization under superatmospheric pressure, an absolutepressure of up to 20 bar is generally set. However, it is preferable tooperate the devolatilization sections under atmospheric pressure.

The number of devolatilization sections and the number, arrangement anddimensions of the devolatilization orifices depend on the water contentof the polymer entering the devolatilization sections and on the desiredwater content of the end product. In a preferred embodiment, an extruderhaving two devolatilization sections is used.

The devolatilization orifices of the devolatilization sections can beprovided with apparatuses, for example retaining screws, which preventthe conveyed material from emerging from the extruder through theorifices. However, such apparatuses are preferably not used.

Following the removal of a part of the residual water contained in theelastomer component A in the squeeze sections 3 and 3', from about 10 to80, preferably from 20 to 75, % by weight of the residual watercontained in the elastomer component A before extrusion are removed inall devolatilization sections 6 and 6' together.

In the region of the devolatilization sections, the extruder screws aregenerally in the form of conventional conveying screws, as described forthe metering sections. It can, however, be useful to incorporatekneading or mixing elements into the screws in the region between thedevolatilization orifices, in order to replace energy consumed inevaporating the water.

In a preferred embodiment, the extruder has, between the lastdevolatilization section and the discharge zone 8, a further section 7in which the components C and/or D (or proportions of the total addedamount of components C and/or D) are fed to the extruder, eithertogether or separately from one another, by at least one metering means.The further section 7 is accordingly located directly before thedischarge zone 8.

This further section 7 is provided with mixing and/or kneading elements,as mentioned by way of example for the plastication sections. Theseelements homogenize the polymer blend. The metering means required forfeeding in C and/or D have also already been described.

Kneading blocks having nonconveying kneading disks and/or kneadingblocks having a conveying pitch, kneading blocks having different landwidths, toothed mixing elements and melt mixing elements are preferablyused as mixing and/or kneading elements, and extruders having one or twoscrews (ie. side extruders) and/or pumps, in paraticular melt pumps, arepreferably used as metering means.

In a preferred embodiment, the total amount of the components C and/or Dwhich are to be introduced into the extruder is fed to the extruder inone or more of the following sections: devolatilization section 6,further section 7 and metering section 2.

The components C and/or D may be added together through at least onefeed orifice or separately through a plurality of feed orifices.

The last section of the extruder is the discharge zone 8. It consists ofa conveying screw and a closed barrel part which is terminated by adefined discharge orifice. The discharge zone is preferably heated.

A preferably used discharge orifice is a die head which is formed, forexample, as a die plate or die strip, where the dies may have a circular(perforated die plate or strip), slot-like or other shape. The productdischarged as an extrudate in the case of a perforated die plate iscooled, for example in water, and granulated in the usual manner.Particularly where a slot die is used, cube granulation is possible.

In a particular embodiment, instead of the perforated die plate or stripdescribed above, with the otherwise usual combination of extrudatetake-off, water bath and granulator, a particular die head withsubsequent underwater granulation is used. Here, the polymer melt passesthrough a die plate having preferably round holes arranged in a circle,is cut under water by rotating blades and is cooled under water, thepolymer solidifying to more or less round, bead-like particles. Withregard to the arrangement of the holes, however, arrangements other thancircular ones and hole shapes other than round ones are also commonlyused.

In a further embodiment, a hot face cutting method is used instead ofthe discharge via a die strip, cooling in a water bath and granulation,the polymer melt emerging from the die head not being cooled by liquidbut, after emergence from the die head, being comminuted (granulated)while still in the hot state, after brief cooling in air. The resultinggranules are then further cooled or cooled during further processing ifthis is necessary. Further processing in the hot state or directextrusion of sheets, films, pipes and profiles is also possible.

In a further embodiment, underwater extrudate granulation is used, inwhich the melt is discharged as extrudate from a die plate and isimmediately wetted by a stream of water and is then introduced, via asloping plane, into a water bath, and is granulated after cooling.

In a further particular embodiment, the discharge zone 8 is providedwith an apparatus for filtering the melt emerging from the extruder,said apparatus, viewed in the conveying direction, being present beforethe die head. Such apparatuses for continuous melt filtration are knownto a person skilled in the art and are commercially available. Ifnecessary, a conveyor element, for example a melt pump or a screwconveyor, may be installed between discharge zone and melt filtration inorder to build up in the melt the pressure required for passing throughthe filter unit.

The melt emerging from the filtration apparatus is granulated and isfurther processed by another method, as described above.

The water content of the emerging polymer (the extrudate moisturecontent) is as a rule from 0.05 to 1.5% by weight, based on thispolymer. The temperature of the polymer melt emerging from the dischargeorifice is as a rule from 180 to 350° C., depending on the type ofpolymers used. It is advantageous to hold the temperatures low enoughfor the thermal stress on the polymer to be as small as possible,without, however, affecting the satisfactory preparation of the desiredproduct.

As is generally known, the various zones of an extruder can beindividually heated or cooled in order to establish an optimumtemperature profile along the screw axis. Furthermore, it is familiar toa person skilled in the art that the individual sections of the extrudermay usually be of different lengths. To achieve particular productproperties, it may specifically be useful to cool certain parts of theextruder or to control their temperature so that it diverges from thatof the remainder of the extruder.

The temperatures and lengths of the individual sections to be chosen inthe specific case differ depending on the chemical and physicalproperties of the components and their ratios, said properties havingbeen mentioned above by way of example.

The same also applies to the screw speed, which may vary within a widerange. A speed of the extruder screws of from 50 to 1200 rpm may bementioned merely by way of example. A speed range of from 100 to 700 rpmis preferred. It is advantageous to design and to operate the extruderin such a way that mean shear rates of from 15 to 450 s⁻¹ areestablished in the region of the squeeze sections at a screw speed offrom 50 to 1200 rpm. Shear rates of from 35 to 260 s⁻¹ areadvantageously established for the preferred screw speed of from 100 to700 rpm. However, depending on the type, amount and properties of thecomponents used, it may be advantageous to operate at mean shear ratesoutside this range.

The extruder screws may be any commercially available screw, for examplea screw having an external diameter of from 10 to 1000 mm. The screwdiameter which is suitable depends on, for example, the type and amountof the components metered into the extruder. The external diameter ofthe screw may be constant along the extruder or vary within particualrlimits.

Depending on the type and amounts of the components, screws having asmaller flight depth or screws having a larger flight depth (ie.deep-flighted screws) may be used in the extruder. Preference is givento the use of screws having a flight depth ratio D_(Screw), external/D_(Screw), internal of from 1.2 to 1.8, preferably from 1.4 to 1.6, andparticularly preferably from 1.45 to 1.58. A commercially availableembodiment of the extruder which is suitable for the novel process has,for example, a flight depth ratio of 1.55, ie. a large flight depth.

In another embodiment, screws having a medium flight depth, particularlythose having a flight depth ratio of from 1.4 to 1.48, are used. Thisembodiment of the extruder is also commercially available and may beadvantageous for certain components and certain amounts of thecomponents. Screws with flight depth ratios of more than 2 are alsosuitable.

The number of starts n of the screw may vary, in particular with n being1, 2 or 3. Double-flight screws are preferably used. However, screwshaving other numbers of starts or those screws which have sections withdifferent numbers of starts may also be used.

Use may in particular be made of extruder screws in which the flightdepth ratio varies along the screw, there being a relationship betweenthe number of starts and the flight depth ratio (multi-stage screw). Usemay preferably be made of a screw in which the change from 3 to 2 startsis accompanied by a change in the flight depth from a low to a highflight depth ratio.

Any polymer which has elastomeric properties and can be fed into anextruder may be used as the elastomer component A. A mixture ofdifferent elastomer components A may also be used.

In particular, particulate rubbers are used as component A, as mentionedat the outset. Those rubbers which have a grafted-on shell comprisingother, generally nonelastomeric polymers are particularly preferred. Ina preferred embodiment of the invention, the graft rubber types fed tothe extruder as partially dewatered material contain up to 50,particularly preferably from 25 to 40, % by weight of residual water.

One embodiment of the invention consists in a process in which elastomercomponents A used are graft rubbers which have a two-stage or multistagestructure and in which the elastomeric base or graft stages are obtainedby polymerization of one or more of the monomers butadiene, isoprene,chloroprene, styrene, alkylstyrene, C₁ -C₁₀ -alkyl esters of acrylicacid or of methacrylic acid and small amounts of other monomers,including crosslinking monomers, and in which the hard graft stages areobtained by polymerizing one or more of the monomers styrene,alkylstyrene, acrylonitrile and methyl methacrylate.

Graft particles A of polymers based on butadiene/styrene/acrylonitrile,n-butyl acrylate/styrene/acrylonitrile, butadiene/n-butylacrylate/styrene/acrylonitrile, n-butyl acrylate/methyl methacrylate,n-butyl acrylate/styrene/methyl methacrylate,butadiene/styrene/acrylonitrile/methyl methacrylate andbutadiene/n-butyl acrylate/methyl methacrylate/styrene/acrylonitrile arepreferred. Polar monomers carrying up to 10% by weight of functionalgroups or crosslinking monomers may be present as polymerized units inthe core or shell.

In this embodiment, styrene/acrylonitrile (SAN) copolymers, copolymersof α-methylstyrene and acrylonitrile, polystyrene, polymethylmethacrylate, polyvinyl chloride or mixtures of these polymers are usedas thermoplastic polymers B.

SAN polymers, copolymers of α-methylstyrene and acrylonitrile,polymethyl methacrylate (PMMA) or mixtures of these polymers arepreferred.

Polycarbonates, polyalkylene terephthalates, such as polybutyleneterephthalate and polyethylene terephthalate, polyoxymethylene,polymethyl methacrylate, polyphenylene sulfide, polysulfones, polyethersulfones and polyamides and mixtures of these thermoplastics may also beused as thermoplastic polymers B. Thermoplastic elastomers, such asthermoplastic polyurethane (TPU), may furthermore be used as polymer B.

Copolymers based on styrene/maleic anhydride, styrene/imidated maleicanhydride, styrene/maleic anhydride/imidated maleic anhydride,styrene/methyl methacrylate/imidated maleic anhydride, styrene/methylmethacrylate, styrene/methyl methacrylate/maleic anhydride, methylmethacrylate/imidated maleic anhydride, styrene/imidated methylmethacrylate, imidated PMMA or mixtures of these polymers may likewisebe used as component B.

In all stated thermoplastic polymers B, some or all of the styrene maybe replaced by α-methylstyrene or by styrenes alkylated on the nucleusor by acrylonitrile.

Among the last-mentioned polymers B, those based onα-methylstyrene/acrylonitrile, styrene/maleic anhydride, styrene/methylmethacrylate and copolymers containing imidated maleic anhydride arepreferred.

Known examples of the elastomer component A are polymers of conjugateddienes, such as butadiene, having an outer graft shell based on avinylaromatic compound, for example SAN copolymers. Graft rubbers basedon crosslinked polymers of C₁ -C₁₀ -alkyl esters of acrylic acid, suchas n-butyl acrylate or ethylhexyl acrylate, grafted with polymers basedon vinylaromatic compounds, such as SAN copolymers, are also known.Graft rubbers which essentially contain a copolymer of conjugated dienesand C₁ -C₁₀ -alkyl acrylates, for example a butadiene/n-butyl acrylatecopolymer, and an outer graft stage comprising SAN copolymer,polystyrene or PMMA are also conventionally used.

The preparation of such graft rubbers by the usual methods, inparticular by emulsion or suspension polymerization, is known.

Graft rubbers based on SAN-grafted polybutadiene are described, forexample, in DT 24 27 960 and EP-A 258 741, and those based onSAN-grafted poly-n-butyl acrylate are described in German ApplicationDAS 1,260,135 and German Laid-Open Application DOS 3,149,358. Furtherdetails of SAN-grafted poly(butadiene/n-butyl acrylate) mixed rubbersare given in EP-A 62 901.

In the case of the graft rubbers mentioned in the last paragraph,copolymers of styrene and acrylonitrile are used, for example, asthermoplastic polymers B. They are known and some of them are alsocommercially available and have, as a rule, a viscosity number VN(determined according to DIN 53 726 at 25° C., 0.5% strength by weightin dimethylformamide) of from 40 to 160 ml/g, corresponding to anaverage molecular weight M_(w) of from about 40000 to 2000000.

The thermoplastic polymers B are preferably prepared by continuous massor solution polymerization, the melt obtained being fed continuously anddirectly to the extruder, for example by means of a melt pump, ifnecessary after removal of the solvents. However, preparation byemulsion, suspension or precipitation polymerization is also possible,the polymer being separated from the liquid phase in an additionaloperation.

Details of the preparation processes are described, for example inKunststoffhandbuch, Editors R. Vieweg and G. Daumiller, Vol. V"Polystyrol", Carl-Hanser-Verlag, Munich, 1969, page 118 et seq.

If the elastomer component A is an SAN-grafted polybutadiene, a moldingmaterial known as ABS (acrylonitrile/butadiene/styrene) is formed byincorporating the SAN. If an SAN-grafted alkyl acrylate is used ascomponent A, ASA molding materials (acrylonitrile/styrene/acrylate) areformed.

In another embodiment, graft rubbers having a residual water content ofup to 60% by weight and based on polydienes and/or polyalkyl acrylatesas well as SAN and/or PMMA are used, said rubbers being composed of morethan two graft stages.

Examples of such multistage graft particles are particles which containa polydiene and/or polyalkyl acrylate as the core, a polystyrene or SANpolymer as the first shell and another SAN polymer having a differentstyrene: acrylonitrile weight ratio as the second shell, or particlescomprising a polystyrene, polymethyl methacrylate or SAN polymer core, afirst shell of polydiene and/or polyalkyl acrylate and a second shell ofpolystyrene, polymethyl methacrylate or SAN polymer. Further examplesare graft rubbers comprising a polydiene core, one or more polyalkylacrylate shells and one or more polymer shells of polystyrene,polymethyl methacrylate or SAN polymer or similarly composed graftrubbers having an acrylate core and polydiene shells.

Copolymers having a multistage core-shell structure of crosslinked alkylacrylate, styrene and methyl methacrylate and an outer shell of PMMA arealso commonly used. Such multistage graft rubbers are described, forexample, in German Laid-Open Application DOS 3,149,046. Graft rubbersbased on n-butyl acrylate/styrene/methyl methacrylate and having a shellof PMMA are described, for example, in EP-A 512 333, any other prior artcomposition of such graft rubbers also being possible. Such rubbers areused as impact modifiers for polyvinyl chloride and preferably forimpact-resistant PMMA. Once again, the stated SAN copolymers and/or PMMAare used as thermoplastic polymers B. If the elastomer component A is amultishell core/shell polymer based on n-butyl acrylate/methylmethacrylate and the polymer B is PMMA, impact-resistant PMMA isaccordingly obtained. In this embodiment too, preferred components B arethe stated SAN copolymers, polystyrene and/or PMMA.

The diameter of the particulate graft rubbers A is generally from 0.05to 20 μm. If these are the generally known graft rubbers of smalldiameter, the diameter is preferably from 0.08 to 1.5 μm, particularlypreferably from 0.1 to 0.8 μm.

In the large-particled graft rubbers prepared for example by means ofsuspension polymerization, the diameter is preferably from 1.8 to 18 μm,in particular from 2 to 15 μm. Such graft rubbers of large diameter aredescribed, for example, in German Laid-Open Application DOS 4,443,886.

The particle size distribution of the graft rubber particles may benarrow or broad and may have one maximum (monomodal) or else two maxima(bimodal). Particle size distributions having more than two maxima arealso possible.

The components C are further polymers, in particular thermoplasticpolymers. Suitable components C are all polymers which were mentionedfor the thermoplastic polymer B. If the components B and C areidentical, the component C is fed to the extruder at another point thanthe component B.

If the monomers of which the polymers B and C are composed areidentical, the components B and C may differ with respect to the amountsof the monomers--for example the polymers B and C may bestyrene/acrylonitrile copolymers which differ in thestyrene:acrylonitrile ratio. If the amounts of the monomers are alsoidentical, the polymers B and C may have different average molecularweights M_(w) (B) and M_(w) (C), measurable, for example, as differentviscosity numbers VN(B) and VN(C).

In addition to the monomers mentioned inter alia for the component B,ie. styrene, acrylonitrile, methyl methacrylate and vinyl chloride, thefollowing other compounds may also be used as essential monomers for thepreparation of C:

α-methylstyrene and styrenes or α-methylstyrenes each of which issubstituted on the nucleus by C₁ -C₈ -alkyl

methacrylonitrile

C₁ -C₂₀ -alkyl esters of acrylic acid and of methacrylic acid

maleic acid, maleic anhydride and maleimides

vinyl ethers and vinylformamide.

Polymers based on α-methylstyrene/acrylonitrile and methylmethacrylate/alkyl acrylate, and copolymers of alkyl esters of acrylicacid or of methacrylic acid and styrene or acrylonitrile or styrene andacrylonitrile are examples of the component C.

Further preferred polymers C are

styrene/acrylonitrile copolymers having different amounts of themonomers compared with the component B, or different average molecularweights M_(w),

copolymers of α-methylstyrene and acrylonitrile,

polymethyl methacrylates,

polycarbonates,

polybutylene terephthalate and polyethylene terephthalate,

polyamides,

copolymers of at least two of the monomers styrene, methyl methacrylate,maleic anhydride, acrylonitrile and maleimides, for example copolymersof styrene, maleic anhydride and phenylmaleimide,

impact-modified polystyrene (HIPS), the rubber component of the HIPSthat is used being, in particular, polybutadiene,

ABS prepared by means of mass polymerization or solution polymerization,

thermoplastic polyurethanes(TPU).

The preparation of these polymers is known to a person skilled in theart and is therefore discussed only briefly below.

Polymethyl methacrylates are to be understood as meaning in particularpolymethyl methacrylate (PMMA) and copolymers based on methylmethacrylate with up to 40% by weight of further copolymerizablemonomers, as obtainable, for example, under the names Lucryl® from BASFAktiengesellschaft or Plexiglas® from Rohm GmbH. A copolymer of 98% byweight of methyl methacrylate and 2% by weight of methyl acrylate as acomonomer may be mentioned merely by way of example (Plexiglas® 8N, fromRohm). A copolymer of methyl methacrylate with styrene and maleicanhydride as comonomers is also suitable (Plexiglas® HW55, from Rohm).

Suitable polycarbonates are known per se. They are obtainable byinterfacial polycondensation, for example by the processes of DE-B-1 300266, or by reacting diphenyl carbonate with bisphenols according to theprocess of DE-A-14 95 730. A preferred bisphenol is2,2-di(4-hydroxyphenyl)propane, generally referred to as bisphenol A.

Instead of bisphenol A, it is also possible to use other aromaticdihydroxy compounds, in particular 2,2-di(4-hydroxyphenyl)pentane,2,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl sulfone,4,4'-dihydroxydihenyl [sic] ether, 4,4'-dihydroxydiphenyl sulfite,4,4'-dihydroxydiphenylmethane, 1,1-di(4-hydroxyphenyl)ethane or4,4'-dihydroxybiphenyl or mixtures of the abovementioned dihydroxycompounds.

Particularly preferred polycarbonates are those based on bisphenol A oron bisphenol A together with up to 30 mol % of the abovementionedaromatic dihydroxy compounds.

Polycarbonates are obtainable, for example, under the trade namesMakrolon® (from Bayer), Lexan® (from General Electric), Panlite® (fromTejin) or Calibre® (from Dow). The relative viscosity of thesepolycarbonates is in general from 1.1 to 1.5, in particular from 1.28 to1.4 (measured at 25° C. in a 0.5% strength by weight solution indichloromethane).

Polybutylene terephthalate and polyethylene terephthalate are preparedas a rule in a manner known per se, by condensation of terephthalic acidor esters thereof with butanediol or ethanediol under catalysis. Thecondensation is advantageously carried out in two stages(precondensation and polycondensation). Details are to be found, forexample, in Ullmann's Encyclopadie der Technischen Chemie, 4th Edition,Volume 19, pages 61-88. Polybutylene terephthalate is commerciallyavailable, for example, as Ultradur® (from BASF).

Preferred polyamides are very generally those having an aliphaticsemicrystalline or partly aromatic and amorphous structure of any type,and blends thereof. Appropriate products are available, for example,under the trade name Ultramid® (from BASF).

The preparation of rubber-modified, impact-modified polystyrene (HIPS)is known to the person skilled in the art. A polybutadiene rubber isgenerally dissolved in monomeric styrene and the resultant solution ofpolybutadiene in styrene is then polymerized. The polymerization is, forexample, carried out in two steps, the step frequently termedprepolymerization being carried out in a first reactor and thesubsequent main polymerization in a subsequent reactor. Thepolymerization initiators used are the usual free-radical generators,but redox systems may also be used. Additionally molecular weightregulators, for example, may be among the ingredients. The preparationis generally carried out either by the continuous solution process (bothsteps in solution) or batchwise by the process frequently termed thebulk/suspension process (first step in bulk, second step in suspension).Details may be found, for example, in U.S. Pat. No. 4,362,850 andUllmanns Encyclopedia of Technical Chemistry, Vol. A21, p. 644-647. Aprocess for continuous solution polymerization of the ABS is alsodescribed in EP-A 477 764.

Polymers prepared by solution polymerization are known per se. Graftpolymers consisting of solution ABS generally have a average particlediameter d₅₀ of from 700 to 20,000 nm, preferably from 1000 to 15,000nm, and are thus markedly larger than ABS graft particles prepared bythe emulsion polymerization process which is otherwise usually used orby other polymerization processes.

In the solution polymerization process, in contrast to suspension oremulsion polymerization, both the monomers and the polymers producedfrom them are dissolved in the selected solvent. Solution ABS isgenerally prepared in a manner similar to the preparation ofrubber-modified, impact-modified polystyrene. A polybutadiene rubber isgenerally dissolved in a mixture of monomeric styrene and monomericacrylonitrile, and the resultant solution of polybutadiene instyrene/acrylonitrile is then polymerized. The polymerization is, forexample, carried out in two steps, the step frequently termedprepolymerization being carried out in a first reactor and thesubsequent main polymerization in a subsequent reactor. Thepolymerization initiators used are the usual free-radical generators,but redox systems may also be used. Additionally molecular weightregulators, for example, may be among the ingredients. The preparationis generally carried out either by the continuous solution process (bothsteps in solution) or batchwise by the process frequently termed thebulk/suspension process (first step in bulk, second step in suspension).Details may be found, for example, in U.S. Pat. No. 4,362,850 andUllmanns Encyclopedia of Technical Chemistry, Vol. A21, p. 644-647. Aprocess for continuous solution polymerization of the ABS is alsodescribed in EP-A 477 764.

Thermoplastic polyurethanes are usually prepared by reacting organic,preferably aromatic, diisocyanates, such as diphenylmethane4,4'-diisocyanate, with polyhydroxy compounds which are preferablyessentially linear, for example polyetherols, or polyesterols, such aspolyalkylene glycol polyadipates, and diols acting as chain extenders,such as butane-1,4-diol, in the presence of catalysts, for exampletertiary amines (such as triethylamine) or organic metal compounds.

The ratio of NCO groups of the diisocyanates to the sum of the OH groups(from the polyhydroxy compounds and chain-extending diols) is preferablyabout 1:1.

The preparation of the TPU is preferably carried out by the belt processin which the stated components and the catalyst are mixed continuouslyby means of a mixing head and the reaction mixture is applied to aconveyor belt. The belt passes through a zone heated to 60-200° C., themixture undergoing reaction and solidifying.

Details of the TPU are to be found, for example, in EP-A 443 432. TPUare available, for example, under the trade name Elastollan® (fromElastogran).

Component C may furthermore essentially comprise copolymers of C₂ -C₈-alkenes, such as ethylene, propene and butene with

vinylaromatics,

polar comonomers, such as acrylic acid and methacrylic acid, the C₁ -C₁₀-alkyl esters of acrylic acid and of methacrylic acid,

other mono- or polyfunctional ethylenically unsaturated acids, such asmaleic acid, maleic anhydride, fumaric acid, itaconic acid and estersthereof, in particular glycidyl esters, esters with C₁ -C₈ -alkanols andesters with aryl-substituted C₁ -C₈ -alkanols,

carbon monoxide,

nonaromatic vinyl compounds, such as vinyl acetate, vinyl propionate andvinyl alkyl ethers,

basic monomers, such as hydroxyethyl acrylate, dimethylaminoethylacrylate, vinylcarbazole, vinylaniline, vinylcaprolactam,vinylpyrrolidone, vinylimidazole and vinylformamide,

acrylonitrile, methacrylonitrile,

which are prepared in a generally known manner.

In a preferred embodiment, a polymer C which can be prepared from 40-75%by weight of ethylene, 5-20% by weight of carbon monoxide and 20-40% byweight of n-butyl acrylate is used (commercially available as Elvaloy®HP-4051 (from DuPont), or a polymer which can be prepared from 50-98.9%by weight of ethylene, 1-45% by weight of n-butyl acrylate and 0.1-20%by weight of one or more compounds selected from the group consisting ofacrylic acid, methacrylic acid and maleic anhydride. The preparation ofthe last-mentioned embodiments is usually carried out by free radicalpolymerization and is described in U.S. Pat. No. 2,897,183 and U.S. Pat.No. 5,057,593.

Copolymers of butadiene (or substituted butadienes) with comonomers,preferably, for instance, styrene, methyl methacrylate or acrylonitrileare also suitable, for example nitrile rubber (NBR) or styrene/butadienerubber (SBR). Some or all of the olefinic double bonds in thesecopolymers may have been hydrogenated.

Other suitable components C are butadiene/styrene copolymers which haveblock structures and are nonhydrogenated, hydrogenated or partiallyhydrogenated. They are preferably prepared by the method of anionicpolymerization in solution using organometallic compounds, such assec-butyllithium, linear block rubbers being formed, for example thosehaving the structure styrene/butadiene (two-block) orstyrene/butadiene/styrene (three-block). These blocks may be separatedfrom one another by polymers having a random distribution, andfurthermore the blocks may also contain minor amounts of units of therespective other monomers.

The presence of small amounts of an ether, in particular tetrahydrofuran(THF), in addition to the initiator, results in the formation of polymerchains which, starting from a butadiene-rich initial segment, have anincreasing styrene content along the chain and finally end in ahomopolystyrene terminal segment. Details of the preparation process aredescribed in DE-A 31 06 959. Polymers C which have such a compositionmay be hydrogenated or partially hydrogenated are also suitable.

Other suitable components C are polymers having a star-like structurewhich are obtained by linking a plurality of polymer chains, mainlythree-block polymers of the type styrene/butadiene/styrene, viapolyfunctional molecules. Suitable linking agents are, for example,polyepoxides, for example epoxidated linseed oil, polyisocyanates, suchas 1,2,4-triisocyanatobenzene, polyketones, such as 1,3,6-hexanetrione,and polyanhydrides, as well as dicarboxylic esters, such as diethyladipate, and silicon halides, such as SiCl₄, metal halides, such asTiCl₄, and polyvinylaromatics, such as divinylbenzenes. Further detailsof the preparation of these polymers are to be found in, for example,DE-A 26 10 068.

It is also possible to use mixtures of at least two of the polymerspreviously stated for C as component C.

In addition to the elastomer component A and polymers B and C, themolding materials prepared by the novel process may contain, as furthercomponent D, additives, for example waxes, plasticizers, lubricants andmold release agents, pigments, dyes, dulling agents, flameproofingagents, antioxidants, light stabilizers and heat stabilizers, fibrousand pulverulent fillers and reinforcing agents and antistatic agents inthe usual amounts for these agents.

The additives D may be present in pure form and in the solid, liquid orgaseous state or may be used as a mixture of the pure substances withone another. They may also be used in a formulation which facilitatesmetering, for example as a solution or as a dispersion (emulsion orsuspension). A formulation in the form of a masterbatch, ie. aconcentrated mixture with a thermoplastic polymer compatible with theextruder content, is also suitable and is preferred in many cases.

The polymers C and the additives D can be fed to the extruder in one ormore of the stated extruder sections. In a preferred embodiment, thecomponents C and D are introduced into the extruder--separately from theelastomer component A and the thermoplastic polymer B--in vent section1, in metering section 2 and/or in section 4 in which the polymer is fedto the extruder. In a further preferred embodiment, the components Cand/or D are fed to the extruder in a further section 7.

The components C and D can be metered into the same section or sectionsor each into different extruder sections, and both 100% of C and 100% ofD may be fed to the extruder in one section or distributed over aplurality of sections.

The exact embodiment of the feed of C and D depends on the statedphysical and chemical properties of the components A to D and on theirratios. For example, it is possible for additives D having low heatresistance not to be fed to the extruder until the discharge zone, withthe result that thermal degradation of the substances D is substantiallyprevented.

The thermoplastic molding materials prepared by the process can beprocessed by the generally conventional methods to give moldings.Examples are extrusion (for pipes, profiles, fibers, films and sheets),injection molding (for shaped articles of all kinds) and calendering androlling (for sheets and films).

An important advantage of the novel process is that a considerable partof the residual water which is present in the partially dewateredelastomer component A is mechanically removed as early as the squeezezones, so that less thermal energy need be used in the downstreamextruder sections for evaporating the remaining water. A substantialenergy saving results.

A further advantage of the novel process is that the extruder can beoperated at low [sic] temperatures than, for example, in the processdescribed in EP-A 534 235, so that the elastomer component A and thepolymers consisting of the components A, B, C and D are processed in agentler manner. Furthermore it is generally possible to dispense withpressure-generating screw elements in the devolatilization part, whichsubject the polymer to considerable thermal and mechanical stress.

By incorporating a partially dewatered elastomer component A into themelt of a thermoplastic polymer B and mixing in further polymers C andadditives D, it is possible to prepare rubber-modified thermoplasticmolding materials of very different types and containing very differentadditives with a high throughput in a single process step, assumingcompatibility or at least partial compatibility of the elastomercomponent with the other components and sufficient heat stability. Inparticular, a very wide range of polymer blends can be prepared bymixing in further polymers C. Because the process makes it possible tofeed the polymer B to the extruder at either one or more points, theproduct properties can be changed advantageously.

Compared with the prior art processes, the novel process furthermore hasthe advantage that no Seiher housings susceptible to blockage are used.This makes it possible to operate the process over a long time withoutthe extruder having to be switched off, cleaned and started up againowing to blockages in the dewatering zone.

The novel arrangement of the extruder can be assembled in an economicalmanner with the aid of commercial extruder components according to themodular principle. Such components are available in the form of screwsections of different designs and associated barrel sections, and permitexact adaptation of the extruder to the specific compounding problem.

EXAMPLES

Screw is to be understood in each case as meaning a twin screw rotatingin the same direction. The designation of the extruder sections which isused in the description is stated in brackets.

a) Extruder configuration I

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer componentA).

Section 2: Length 4 D, unheated, with dewatering orifice at the top(bore in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), which isprovided with a retaining screw, and conveying screw (Squeeze section 3,front part).

Section 3: Length 4 D, unheated, without orifices, contains kneadingblock and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in Section 2 is 3 D (Squeeze section 3,rear part).

Section 4: Length 4 D, unheated, without orifices and with conveyingscrew.

Section 5: Length 4 D, heated, with lateral orifice through which themelt of polymer B is introduced by means of a ZSK 53 side extruder (fromWerner and Pfleiderer);

the screw of the main extruder contains conveying elements and kneadingblocks (Section 4, in which the melt of the thermoplastic polymer B isfed in).

Section 6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (Second devolatilization section 6').

Sections 9-12: Length 4 D each, heated, without orifices and withconveying screw (Discharge zone 8, front part)

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

b) Extruder configuration II

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer componentA).

Section 2: Length 4 D, unheated, with dewatering orifice at the top(bore in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), which isprovided with a retaining screw, and conveying screw (Squeeze section 3,front part).

Section 3: Length 4 D, unheated, without orifices, contains kneadingblock and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in Section 2 is 3 D (Squeeze section 3,rear part).

Section 4: Length 4 D, unheated, without orifices and with conveyingscrew.

Section 5: Length 4 D, heated, with lateral orifice through which themelt of polymer B is introduced by means of a ZSK 53 side extruder (fromWerner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Section 4, in which the melt ofthe thermoplastic polymer B is fed in).

Section 6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plasticating section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (Second devolatilization section 6').

Section 9: Length 4 D, heated, with lateral metering orifice which isprovided with a ZSK 25 or ZSK 53 side extruder (depending on throughput,from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Further section 7 in which thecomponents C and/or D are fed in, front part)

Section 10: Length 4 D, heated, with orifice at the top which isprovided with an inlet connection; Screw with kneading blocks (Furthersection 7 in which the components C and/or D are fed in, rear part)

Sections 11-12: Length 4 D each, heated, without orifices and withconveying screw (Discharge zone 8, front part).

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

c) Extruder configuration III

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer componentA).

Section 2: Length 4 D, unheated, with dewatering orifice at the top(bore in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), which isprovided with a retaining screw, and conveying screw (First squeezesection 3, front part).

Section 3: Length 4 D, unheated, without orifices, contains kneadingblock and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in Section 2 is 3 D (First squeeze section3, rear part).

Section 4: Length 4 D, unheated, with dewatering orifice at the top(bore in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), which isprovided with a retaining screw, and conveying screw (Second squeezesection 3', front part).

Section 5: Length 4 D, unheated, without orifices, contains kneadingblock and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in Section 4 is 3 D. (Second squeezesection 3', rear part).

Section 6: Length 4 D, heated, with lateral orifice through which themelt of the polymer B is introduced by means of a ZSK 53 side extruder(from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks. (Section 4 in which the melt ofthe thermoplastic polymer B is fed in).

Section 7: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (Second devolatilization section 6).

Section 9: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (Second devolatilization section 6').

Section 10: Length 4 D, heated, with lateral metering orifice which isprovided with a ZSK 25 side extruder (from Werner & Pfleiderer); thescrew of the main section contains conveying elements and kneadingblocks (Further section 7 in which the components C and/or D are fed in,front part).

Section 11: Length 4 D, heated, with orifice at the top which isprovided with an inlet connection; screw with kneading blocks (Furthersection 7 in which the components C and/or D are fed in, rear part).

Section 12: Length 4 D, heated, without orifices and with conveyingscrew (Discharge zone 8, front part).

Termination: The strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

d) Extruder configuration IV

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer component A,forward part).

Section 2: Length 4 D, unheated, without orifices, with conveying screw(Metering section 2 for elastomer component A, rear part).

Section 3: Length 4 D, unheated, with dewatering orifice at the top(hole in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction) contains, asretarding elements, kneading block and thread opposite to the conveyingdirection; the distance between the first retarding element and theassociated dewatering orifice is 1.5 D (First squeeze section 3).

Section 4: Length 4 D, unheated, with dewatering orifice at the top(hole in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), provided with aretaining screw, contains conveying screw and, as retarding elements,kneading block and thread opposite to the conveying direction; thedistance between the first retarding element and the associateddewatering orifice is 1.5 D (Second squeeze section 3').

Section 5: Length 4 D, heated, with lateral orifice through which themelt of polymer B is introduced by means of a ZSK 53 side extruder (fromWerner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Section 4, in which the melt ofthe thermoplastic polymer B is fed in).

Section 6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, and kneading block between the two devolatilizationorifices, devolatilization is operated under atmospheric pressure(Second devolatilization section 6').

Section 9: Length 4 D, heated, with lateral metering orifice which isprovided with a ZSK 25 or ZSK 53 side extruder (depending on throughput,from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Further section 7 in which thecomponents C and/or D are fed in, front part)

Section 10: Length 4 D, heated, with orifice at the top which isprovided with an inlet connection; screw with kneading blocks (Furthersection 7 in which the components C and/or D are fed in, rear part)

Sections 11-12: Length 4 D each, heated, without orifices and withconveying screw (Discharge zone 8, front part).

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

e) Extruder configuration V

A twin-screw extruder of the type ZSK 58 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 10 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer componentA).

Section 2: Length 4 D, unheated, with dewatering orifice at the top(hole in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), provided with aretaining screw, and conveying screw, and kneading block and threadopposite to the conveying direction as retarding elements; the distancebetween the first retarding element and the associated dewateringorifice in section 2 is 1 D (First squeeze section 3).

Section 3: Length 4 D, unheated, with dewatering orifice at the top(hole in extruder barrel in the form of a horizontal figure eight withits longitudinal axis in the conveying direction), provided with aretaining screw, and conveying screw (Second squeeze section 3', frontpart).

Section 4: Length 4 D, unheated, without orifices, contains kneadingblocks and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in section 3 is 3 D (Second squeezesection 3', rear part).

Section 5: Length 4 D, heated, with lateral orifice through which themelt of the polymer B is introduced by means of a ZSK 53 side extruder(from Werner and Pfleiderer); the screw of the main extruder containsneutral and conveying elements and kneading blocks (Section 4, in whichthe melt of the thermoplastic polymer B is fed in).

Section 6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw and kneading block between the two devolatilizationorifices, devolatilization is operated at atmospheric pressure (Seconddevolatilization section 6').

Section 9+10: Length 4 D each, heated, without orifices and withconveying screw (Discharge zone 8, front part).

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart). The screw diameter is D=58 mm. The screw is deep-flighted (largeflight depth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

f) Extruder configuration VI

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer component A,front part).

Section 2: Length 4 D, unheated, without orifices, with conveying screwand a kneading block with back-conveying pitch (metering section 2 forelastomer component A, rear part).

Section 3: Length 4 D, unheated, with dewatering orifice at the top(hole in extruder barrel in the form of a horizontal figure eight withits longitudinal axis in the conveying direction), contains a shorttransition zone with a length of 0.6 D as retarding elements, a kneadingblock and a thread opposite to the conveying direction; the distancebetween the first retarding element and the associated dewateringorifice is 1.6 D (First squeeze section 3).

Section 4: Length 4 D, unheated, with dewatering orifice at the top(hole in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), provided with aretaining screw, contains conveying screw and kneading block and threadopposite to the conveying direction as retarding elements; the distancebetween the first retarding element and the associated dewateringorifice is 1.5 D (Second squeeze section 3').

Section 5: Length 4 D, heated, with lateral orifice through which themelt of the polymer B is introduced by means of a ZSK 53 side extruder(from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Section 4 in which the melt ofthe thermoplastic polymer B is fed in).

Section 6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, and kneading block between the two devolatilizationorifices, devolatilization is operated under atmospheric pressure(Second devolatilization section 6').

Section 9: Length 4 D, heated, with lateral metering orifice which isprovided with a ZSK 25 or ZSK 53 side extruder (depending on throughput,from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and toothed mixing elements (Further section 7 inwhich the components C and/or D are fed in, front part)

Section 10-12: Length 4 D each, heated, without orifices and withconveying screw (Discharge zone 8, front part).

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

g) Extruder configuration VII

A twin-screw extruder of the type ZSK 40 from Werner and Pfleiderer,Stuttgart, was used, said extruder consisting of 12 sections. Theirarrangement in the downstream direction was as follows:

Section 1: Length 4 D, unheated, with metering orifice at the top, whichis provided with a metering means ESB 45 from Werner and Pfleiderer, andneutrally conveying screw (Metering section 2 for elastomer componentA).

Section 2: Length 4 D, unheated, with dewatering orifice at the top(hole in the extruder barrel in the form of a horizontal figure eightwith its longitudinal axis in the conveying direction), provided with aretaining screw, and conveying screw (Squeeze section 3, front part).

Section 3: Length 4 D, unheated, without orifices, contains kneadingblock and thread opposite to the conveying direction as retardingelements; the distance between the first retarding element and theassociated dewatering orifice in section 2 is 3 D (Squeeze section 3,rear part).

Section 4: Length 4 D, heated, with lateral orifice through which themelt of the polymer B is introduced by means of a ZSK 53 side extruder(from Werner and Pfleiderer); the screw of the main extruder containsconveying elements and kneading blocks (Section 4 in which the melt ofthe thermoplastic polymer B is fed in).

Section 5-6: Length 4 D, heated, without orifices, with a screw sectionwhich contains kneading blocks (Plastication section 5).

Section 7: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, devolatilization is operated under atmosphericpressure (First devolatilization section 6).

Section 8: Length 4 D, heated, with devolatilization orifice at the topand conveying screw, and kneading block between the two devolatilizationorifices, devolatilization is operated under atmospheric pressure(Second devolatilization section 6', front part).

Section 9: Length 4 D, heated, without orifices, screw containsconveying elements and kneading blocks (Second devolatilization section6', rear part).

Section 10-11: Length 4 D, heated, without orifice, screw with kneadingblocks (Discharge zone 8, front part)

Section 12: Length 4 D each, heated, without orifices and with conveyingscrew (Discharge zone 8, middle part).

Termination: Die strip with cylindrical holes (Discharge zone 8, rearpart).

The screw diameter is D=40 mm. The screw is deep-flighted (large flightdepth) and the flight depth ratio D_(Screw), external /D_(Screw),internal is 1.55. The screw has a two-flight design.

h) Polymer components used

The following graft rubbers were used as elastomer component A:

A-1: Graft copolymer comprising 5 stages based on methyl methacrylate orn-butyl acrylate

A graft polymer was prepared from 5 different hard or soft stages inemulsion. The specific procedure was as described in EP-A 512 333,Example 1, Table 1 on page 8.

1st stage (hard core): Methyl methacrylate+ethyl acrylate+alkylmethacrylate

2nd stage (soft first shell): n-Butyl acrylate+styrene+alkylmethacrylate

3rd stage (hard second shell): Methyl methacrylate+ethyl acrylate+allylmethacrylate

4th stage (soft third shell): n-Butyl acrylate+styrene+allylmethacrylate

5th stage (hard fourth shell): Methyl methacrylate+ethyl acrylate.

The monomer stated first for each stage is the main monomer in terms ofquantity. The precipitated graft polymer was filtered off with suctionand dewatered by means of a pilot-scale centrifuge to the water contentstated in the Tables.

A-2: Graft polymer based on butadiene and n-butyl acrylate, grafted withSAN

A mixture of vinyl methyl ether, n-butyl acrylate and butadiene waspolymerized in emulsion and the latex was agglomerated (average particlesize d₅₀ :310 nm). Graft polymerization was then carried out with astyrene/acrylonitrile mixture. Further details are given in EP-A 62 901,page 11, line 1 to page 12, line 14 (Example 2), the precipitated graftpolymer being filtered off with suction and dewatered by means of apilot-scale centrifuge to the water content stated in the Tables.

A-3: Graft polymer based on butadiene, grafted with SAN

Butadiene was polymerized in emulsion, the latex obtained wasagglomerated, a latex having an average particle size d₅₀ of 238 nmbeing formed, and graft polymerization was then effected with a mixtureof styrene and acrylonitrile. Further details are given in GermanPublished Application DAS 2,427,960, column 6, line 17 to column 7, line27, the precipitated graft polymer being dewatered by means of apilot-scale centrifuge to the water content stated in the Tables.

A-4: Graft polymer based on n-butyl acrylate, grafted with SAN

n-Butyl acrylate was polymerized with a crosslinking agent in emulsionto give a latex having an average particle diameter d₅₀ of 123 nm. Astyrene/acrylonitrile mixture was graft-polymerized onto this latex.Further details are given in EP-A 450 485, column 7, lines 10-24(Example A), dewatering being carried out by centrifuging to the watercontent stated in the Tables.

A-5: Graft rubber based on n-butyl acrylate, grafted with styrene andSAN

n-Butyl acrylate was polymerized with a crosslinking agent in emulsionin two steps to give a latex having an average particle diameter d₅₀ of410 nm. A first stage comprising polystyrene and a second stagecomprising styrene/acrylonitrile copolymer were graft-polymerized ontothis latex. With regard to the details, reference may be made to GermanLaid-Open Application DOS 3,149,358, page 15, line 12 to page 16, line24, dewatering being effected by centrifuging to the water contentstated in the Tables.

The following polymers were used as thermoplastic polymers B:

B-1: Polymethyl methacrylate

A mixture of 99% by weight of methyl methacrylate and 1% by weight ofmethyl acrylate was polymerized in suspension as described in EP-A 489318, page 4, line 52 et seq., according to Example 6 (Table on page 7).The viscosity number VN (determined according to DIN 53726 at 25° C.,0.26% strength by weight in chloroform) was 74 ml/g.

B-2: Polymethyl methacrylate

A mixture of 96% by weight of methyl methacrylate and 4% by weight ofmethyl acrylate was polymerized as described under B-1. The viscositynumber VN (determined as in the case of B-1) was 56 ml/g.

B-3: Styrene/acrylonitrile copolymer

A mixture of 75% by weight of styrene and 25% by weight of acrylonitrilewas prepared by the continuous solution polymerization method, asdescribed in Kunststoff-Handbuch, Editors Vieweg and Daumiller, Vol. V"Polystyrol", Hanser-Verlag Munich 1969, pages 122-124. The viscositynumber VN (determined according to DIN 53726 at 25° C., 0.5% strength byweight in dimethylformamide) was 70 ml/g.

B-4: Styrene/acrylonitrile copolymer

The procedure was as described under B-3, except that a different degreeof polymerization was established. The viscosity number (determined asin the case of B-3) was 100 ml/g.

B-5: Styrene/acrylonitrile copolymer

A mixture of 65% by weight of styrene and 35% by weight of acrylonitrilewas polymerized as described in the case of B-3. The viscosity number(determined as in the case of B-3) was 80 ml/g.

B-6: Styrene/acrylonitrile copolymer

The procedure was as described under B-5, except that a different degreeof polymerization was established. The viscosity number (determined asin the case of B-3) was 60 ml/g.

B-7: Identical to the α-methylstyrene/acrylonitrile copolymer ofcomponent C-1.

B-8: Identical to the polycarbonate of component C-3.

B-9: Identical to the solution ABS component C-8.

The following polymers were used as further polymer C:

C-1: α-Methylstyrene/acrylonitrile copolymer

A copolymer of 70% by weight of α-methylstyrene and 30% by weight ofacrylonitrile was prepared as described for polymer B. The viscositynumber VN (determined as in the case of B-3) was 56 ml/g.

C-2: Ethylene/n-butyl acrylate/carbon monoxide copolymer

A copolymer of about 55% by weight of ethylene, about 15% by weight ofcarbon monoxide and about 30% by weight of n-butyl acrylate was used,said copolymer being commercially available as Elvaloy® HP-4051 (fromDuPont).

C-3: Polycarbonate

A commercial product based on bisphenol A was used (Makrolon® R2800 fromBayer). The viscosity number (determined according to DIN 53726 at 23°C., 0.5% strength by weight in dichloromethane) was 61.4 ml/g.

C-4: Imidated copolymer of styrene and maleic anhydride

A commercial product was used. It consisted of 58 mol % of styrene and42 mol % of maleic anhydride and was imidated with aniline so that theproduct contained 1% by weight of free maleic anhydride groups. Thecommercial product Malekka® MS-NA (from Denka Chemicals) was used. Itsaverage molecular weight M_(w) was 135000.

C-5: Identical to the styrene/acrylonitrile copolymer of component B-6

C-6: Identical to the polymethyl methacrylate of component B-2

C-7: Identical to the styrene/acrylonitrile copolymer of component B-5

C-8: Acrylonitrile/butadiene/styrene polymer prepared by solutionpolymerization (solution ABS), the polymer containing 23.3% by weight ofcopolymerized acrylonitrile, 69.7% by weight of copolymerized styreneand 7% by weight of polybutadiene rubber. The average particle size d₅₀was 8.7 μm.

C-9: Acrylonitrile/butadiene/styrene polymer prepared by solutionpolymerization (solution ABS), the polymer containing 22.8% by weight ofcopolymerized acrylonitrile, 70.7% by weight of copolymerized styreneand 7% by weight of polybutadiene rubber. The average particle size d₅₀was 9 μm.

The following were used as additives D:

D-1: Tris(nonylphenyl) phosphite (TNPP). The product Irgafos® TNPP (fromCiba-Geigy) was used.

D-2: Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate. Theproduct Irganox® 1076 (from Ciba-Geigy) was used.

D-3: Colorant masterbatch, containing 20% by weight of carbon black and80% by weight of the styrene/acrylonitrile copolymer of component B-1.

D-4: Stabilizer masterbatch, containing 1% by weight ofbis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (the productUltranox® 626 from General Electric Plastics), 1% by weight of octadecyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (the product Irganox®1076 from Ciba-Geigy) and 98% by weight of the polymethyl methacrylateof component B-1.

D-5: Stabilizer masterbatch containing 10% by weight of a stericallyhindered amine (the product Uvinul® 4050H from BASF), 10% by weight ofethyl 2-cyano-3,3'-diphenylacrylate (the product Uvinul® 3035 from BASF)and 80% by weight of the polymethyl methacrylate of component B-1.

D-6: Copolymer of methyl methacrylate, styrene and maleic anhydride.

A commercial product comprising 75% by weight of methyl methacrylate,15% by weight of styrene and 10% by weight of maleic anhydride was used(Plexiglas® HW 55 from Rohm or Degalan® HT 120 from Degussa).

D-7: Masterbatch containing 5% by weight of

1,1,3-tri(2'-methyl-4'-hydroxy-5'-tert-butyl(phenyl)butane [sic], 10% byweight of dilauryl β,β'-thiodipropionate and 85% by weight of thestyrene/acrylonitrile copolymer of component B-5.

D-8: Diisodecyl phthalate

The components A present as a moist powder was [sic] fed to the extrudervia a solids metering means ESB-45, and the melts of the thermoplasticpolymers B by means of a side extruder ZSK 53 (from Werner andPfleiderer). The components C and/or D were present as powder orgranules and were likewise introduced into the extruder by means of aside extruder (ZSK 53 or ZSK 25 from the same manufacturer) or by agranule metering means. The liquid components D-1 and D-8 were fed in bymeans of a pump.

A mixture D* containing 95% by weight of B-1 and 5% by weight of D-2 wasprepared from the components B-5 and D-2 [sic]. This mixture waslikewise introduced into the extruder by means of a side extruder (ZSK25).

i) Measurements

The water discharge and the rubber discharge in the first and secondsqueeze zones and the extrudate moisture content of the emerging endproduct were measured. These measurements were carried outgravimetrically.

The amount of water emerging as steam was determined by calculating thedifference between the initial residual water content and the sum of theliquid water emerging.

Percentages were calculated from the discharges of water, steam andrubber in kg/h. The stated percentages are percentages by weight and,for water and steam, are based on the water content of the rubber fed tothe extruder (lines marked with *), which was made equal to 100, and,for rubber, based on the amount of moist rubber fed in (lines markedwith **), which was made equal to 100. The extrudate moisture content isbased on the end product obtained.

                  TABLE 1                                                         ______________________________________                                        Extruder configuration I                                                        Example          I-1       I-2     I-3                                      ______________________________________                                        Elastomer component A                                                           Type A-1 A-1 A-1                                                              Water content [% by weight]* 37 37 37                                         Feed [kg/h]** 55.6 53.9 57.2                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-2 B-1 B-1                                                              Feed [kg/h] 43.1 44.2 42.0                                                    in Section No. 5 5 5                                                          Further polymer C                                                             Type --  --  --                                                               Feed [kg/h]                                                                   in Section No.                                                                Additives D                                                                   Type  D-4 D-5                                                                 Feed [kg/h] -- 2.0 2.4                                                        in Section No.  1 1                                                           Feed by.sup.3)  GM GM                                                         Extruder:                                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 5-12 250 250 250                                      [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 11.2 = 54% 11.9 = 60% 12.7 = 60%                Rubber discharge [kg/h].sup.2) 1.3 = 2% 1.3 = 2% 1.4 = 2%                     Devolatilization sections  9.2 = 45%  7.8 = 39%  8.3 = 39%                    Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.2 0.2 0.2                                        [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) GM Granule metering                                              

                  TABLE 2                                                         ______________________________________                                        Extruder configuration II                                                     ______________________________________                                        Example        II-1       II-2     II-3                                       ______________________________________                                          Elastomer component A                                                         Type A-2 A-2 A-2                                                              Water content [% by weight]* 28 28 28                                         Feed [kg/h]**  26.0  26.0  26.0                                               in Section No.  1  1  1                                                       Thermoplastic polymer B                                                       Type B-3 B-6 B-4                                                              Feed [kg/h] 79 79 79                                                          in Section No.  5  5  5                                                       Further polymer C                                                             Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Additives D                                                                   Type D-7 D-7 D-7                                                              Feed [kg/h]  3  3  3                                                          in Section No.  9  9  9                                                       Feed by.sup.3) SE SE SE                                                       Extruder (main extruder):                                                     Speed [rpm] 300  300  300                                                     Temperature in Sections 5-12 250  250  250                                    [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 2.0 = 27% 1.9 = 26% 2.7 = 37%                   Rubber discharge [kg/h].sup.2) 0.4 = 2%  0.5 = 2%  0.6 = 2%                   Devolatilization sections 5.3 = 73% 5.4 = 74% 4.6 = 63%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content  <0.1  <0.1  <0.1                                  [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder                                                 

    Example        II-4       II-5     II-6                                       ______________________________________                                          Elastomer component A                                                         Type A-4 A-3 A-2                                                              Water content [% by weight]* 34 28 21                                         Feed [kg/h]**  49.3  34.7  25.0                                               in Section No.  1  1  1                                                       Thermoplastic polymer B                                                       Type B-6 B-6 B-4                                                              Feed [kg/h] 40 75 25                                                          in Section No.  5  5  5                                                       Further polymer C                                                             Type C-5 -- C-6                                                               Feed [kg/h]  8  18                                                            in Section No.  9   9                                                         Feed by.sup.3) SE  SE                                                         Additives D                                                                   Type D-3 D-8 --                                                               Feed [kg/h]  8  2                                                             in Section No.  9 10                                                          Feed by.sup.3) SE MP                                                          Extruder (main extruder):                                                     Speed [rpm] 300  300  300                                                     Temperature in Sections 5-12 250  250  250                                    [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 9.1 = 54% 3.4 = 35% 2.2 = 42%                   Rubber discharge [kg/h].sup.2) 0.5 = 1%  0.7 = 2%  0.3 = 1%                   Devolatilization sections 7.5 = 45% 6.2 = 64% 3.0 = 57%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content   0.2   0.2   0.1                                  [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder, MP Metering pump                               

    Example        II-7       II-8     II-9                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-4 A-3                                                              Water content [% by weight]* 29 33 29                                         Feed [kg/h]**  32.0  44.7  42.4                                               in Section No.  1  1  1                                                       Thermoplastic polymer B                                                       Type B-7 B-8 B-5                                                              Feed [kg/h] 43 60 50                                                          in Section No.  5  5  5                                                       Further polymer C                                                           Type            C-5    C-3    C-5    C-4                                        Feed [kg/h] 9 30 10 20                                                        in Section No. 9  9  9  9                                                     Feed by.sup.3) SE SE SE SE                                                  Additives D                                                                     Type D-6 D-7 D-7                                                              Feed [kg/h]  3  3  3                                                          in Section No.  1  9  9                                                       Feed by.sup.3) GM SE SE                                                       Extruder (main extruder):                                                     Speed [rpm] 300  300  300                                                     Temperature in Sections 5-12 250  250   250.sup.4)                            [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 4.2 = 45% 7.2 = 49% 6.2 = 50%                   Rubber discharge [kg/h].sup.2) 0.8 = 3%  1.0 = 2%  0.9 = 2%                   Devolatilization sections 5.1 = 55% 7.4 = 50% 6.1 = 50%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content  <0.1  0.2  <0.1                                   [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder, GM Granule metering                                 .sup.4) Extruder (main extruder) from Section 9: 280° C., side         extruder: 280° C.                                                 

                  TABLE 3                                                         ______________________________________                                        Extruder configuration III                                                    ______________________________________                                        Example      III-1    III-2        III-3                                      ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-5                                                              Water content 29 29 30                                                        [% by weight]*                                                                Feed [kg/h]** 46.0 38.0 50.0                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-5 B-5                                                              Feed [kg/h] 32 50 46                                                          in Section No. 6 6 6                                                          Further polymer C                                                             Type C-1 --  --                                                               Feed [kg/h] 16                                                                in Section No. 10                                                             Feed by.sup.7) SE                                                             Additives D                                                                 Type         --       D-1    D*.sup.5)                                                                          D-3  D-3                                      Feed [kg/h]  0.4 4.0.sup.6) 10 1.6                                            in Section No.  11 10 10 1                                                    Feed by.sup.7)  MP SE SE SE                                                 Extruder (main extruder):                                                       Speed [rpm] 300 300 300                                                       Temperature in Sections 250 250 250                                           6-12 [° C.]                                                            1st squeeze section                                                           Water discharge [kg/h].sup.1) 3.5 = 26% 2.5 = 23%  9.4 = 63%                  Rubber discharge [kg/h].sup.2) 0.7 = 2%  0.9 = 2%  1.1 = 2%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 2.7 = 20% 3.2 = 29% 0.2 = 1%                    Rubber discharge [kg/h].sup.2) 0.4 = 1%  0.2 = 1%  <0.1 = <1%                 Devolatilization sections 7.1 = 53% 5.2 = 47%  5.4 = 36%                      Steam discharge [kg/h].sup.1)                                                 Extrudate moisture <0.1 0.1 0.2                                               content [% by weight]                                                       ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.5) D* is a mixture of B5 and D2                                          .sup.6) Feed of mixture corresponding to 3.8 kg/h of B5 and 0.2 kg/h of D     .sup.7) SE Side extruder, MP Metering pump                               

    Example        III-4      III-5    III-6                                      ______________________________________                                          Elastomer component A                                                         Type A-5 A-2 A-2                                                              Water content [% by weight]* 35 34 34                                         Feed [kg/h]** 63.0 48.3 47.4                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-5 B-5 B-5                                                              Feed [kg/h] 10 30 30                                                          in Section No. 6 6 6                                                          Further polymer C                                                             Type C-2 C-1 C-1                                                              Feed [kg/h] 6 12 12                                                           in Section No. 1 10 10                                                        Feed by.sup.3) GM SE SE                                                       Additives D                                                                   Type -- -- D-3                                                                Feed [kg/h]   7.3                                                             in Section No.   10                                                           Feed by.sup.3)   SE                                                           Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 6-12 250 250 250                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 15.6 = 71% 6.0 = 37% 5.7 = 35%                  Rubber discharge [kg/h].sup.2) 1.7 = 3% 0.9 = 2%  0.8 = 2%                    2nd squeeze section                                                           Water discharge [kg/h].sup.1)  0.2 = <1% 6.1 = 37% 5.5 = 34%                  Rubber discharge [kg/h].sup.2) <0.1 = <1% 0.7 = 1%  0.8 = 2%                  Devolatilization sections  6.2 = 28% 4.1 = 25% 4.7 = 29%                      Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.2 <0.1 0.1                                       [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder, GM Granule metering                            

    Example        III-7     III-8     III-9                                      ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [% by weight]* 29 29 29                                         Feed [kg/h]** 61.3 42.0 41.0                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-6 B-6                                                              Feed [kg/h] 38 70 46                                                          in Section No. 6 6 6                                                          Further polymer C                                                             Type C-7   C-1                                                                Feed [kg/h] 20 -- 12                                                          in Section No. 10  10                                                         Feed by.sup.3) SE  SE                                                         Additives D                                                                 Type           D-8       D-3    D-8  D-7                                        Feed [kg/h] 0.5 3.0 0.7 3.0                                                   in Section No. 11 10 11 10                                                    Feed by.sup.3) MP SE MP SE                                                  Extruder (main extruder):                                                       Speed [rpm] 300 300 300                                                       Temperature in Sections 6-12 250 250 250                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 5.4 = 30% 3.5 = 29%  5.0 = 42%                  Rubber discharge [kg/h].sup.2) 1.0 = 2%  0.7 = 2%  0.3 = 1%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 3.3 = 19% 1.7 = 14% 0.1 = 1%                    Rubber discharge [kg/h].sup.2) 0.5 = 1%  0.2 = 1%  <0.1 = 1%                  Devolatilization sections 9.0 = 51% 6.8 = 56%  6.8 = 57%                      Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.2 0.2 <0.1                                       [% by weight]                                                               ______________________________________                                        Example            III-10                                                     ______________________________________                                          Elastomer component A                                                         Type A-3                                                                      Water content [% by weight]* 30                                               Feed [kg/h]** 40.0                                                            in Section No. 1                                                              Thermoplastic polymer B                                                       Type B-6                                                                      Feed [kg/h] 38                                                                in Section No. 6                                                              Further polymer C                                                             Type C-5                                                                      Feed [kg/h] 20                                                                in Section No. 10                                                             Feed by.sup.3) SE                                                             Additives D                                                                 Type                   D-3    D-8                                               Feed [kg/h] 2.7 0.6                                                           in Section No. 10 11                                                          Feed by.sup.3) SE MP                                                        Extruder (main extruder):                                                       Speed [rpm] 300                                                               Temperature in Sections 6-12 250                                              [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1)  3.4 = 28%                                      Rubber discharge [kg/h].sup.2) 0.2 = 1%                                       2nd squeeze section                                                           Water discharge [kg/h].sup.1)  1.5 = 13%                                      Rubber discharge [kg/h].sup.2) <0.1 = <1%                                     Devolatilization sections  7.1 = 59%                                          Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1                                               [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder, MP Metering pump                               

                  TABLE 4                                                         ______________________________________                                        Extruder configuration IV                                                     ______________________________________                                        Example        IV-1       IV-2     IV-3                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [% by weight]* 30 30 30                                         Feed [kg/h]** 45.2 45.2 45.2                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-6 B-6                                                              Feed [kg/h] 35.2 17.6 32.5                                                    in Section No. 5 5 5                                                          Further polymer C                                                             Type --  C-5 C-5                                                              Feed [kg/h]  17.6 32.5                                                        in Section No.  9 9                                                           Feed by.sup.3)  SE SE                                                         Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 5-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 4.9 = 36% 5.3 = 39% 6.8 = 50%                   Rubber discharge [kg/h].sup.2) 0.3 = 1%  0.2 = <1% 0.2 = <1%                  2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 8.6 = 63% 8.2 = 61% 6.7 = 49%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1 <0.1 <0.1                                     [% by weight]                                                               ______________________________________                                        Example        IV-4       IV-5     IV-6                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [% by weight]* 30 30 30                                         Feed [kg/h]** 45.2 45.2 37.6                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-5 B-5                                                              Feed [kg/h] 45 40 15                                                          in Section No. 5 5 5                                                          Further polymer C                                                             Type C-5 C-3 C-3                                                              Feed [kg/h] 45 30 60                                                          in Section No. 9 9 9                                                          Feed by.sup.3) SE SE SE                                                       Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 5-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 5.6 = 36% 6.1 = 45% 4.7 = 42%                   Rubber discharge [kg/h].sup.2) 0.2 = 1%  0.3 = 1%  0.2 = 1%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 9.7 = 63% 7.4 = 55% 6.6 = 59%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1 <0.1 <0.1                                     [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder                                                 

                  TABLE 5                                                         ______________________________________                                        Extruder configuration V                                                        Example             V-1       V-2                                           ______________________________________                                        Elastomer component A                                                           Type A-3 A-3                                                                  Water content [% by weight]* 34.9 30.0                                        Feed [kg/h]** 159.1 157.1                                                     in Section No. 1 1                                                            Thermoplastic polymer B                                                       Type B-5 B-5                                                                  Feed [kg/h] 124.2 124.2                                                       in Section No. 5 5                                                            Further polymer C                                                             Type --  --                                                                   Feed [kg/h]                                                                   in Section No.                                                                Feed by                                                                       Additives D                                                                   Type -- --                                                                    Feed [kg/h]                                                                   in Section No.                                                                Feed by                                                                       Extruder (main extruder):                                                     Speed [rpm] 285 285                                                           Temperature in Sections 5-10 250 250                                          [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 25.0 = 45% 9.9 = 21%                            Rubber discharge [kg/h].sup.2) 7.9 = 5% 2.5 = 2%                              2nd squeeze section                                                           Water discharge [kg/h].sup.1)  7.9 = 14% 5.4 = 11%                            Rubber discharge [kg/h].sup.2) 2.4 = 2% 0.1 = <1%                             Devolatilization sections 22.6 = 41% 31.8 = 67%                               Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1 <0.1                                          [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                               

                  TABLE 6                                                         ______________________________________                                        Extruder configuration VI                                                     ______________________________________                                        Example        VI-1       VI-2     VI-3                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [Gew.-%)* 30 25 25                                              Feed [kg/h]** 42.1 42.1 42.1                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-6 B-6                                                              Feed [kg/h] 90 38.2 32.9                                                      in Section No. 5 5 5                                                          Further polymer C                                                             Type   C-5 C-5                                                                Feed [kg/h] -- 72 53.5                                                        in Section No.  9 9                                                           Feed by.sup.3)  SE SE                                                         Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 6-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 4.2 = 33% 3.7 = 35% 3.6 = 34%                   Rubber discharge [kg/h].sup.2) 0.1 = <1% 0.1 = <1% 0.1 = <1%                  2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 8.4 = 67% 6.8 = 64% 6.9 = 65%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.1 <0.1 <0.1                                      [% by weight]                                                               ______________________________________                                        Example        VI-4       VI-5     VI-6                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [Gew.-%]* 25 25 25                                              Feed [kg/h]** 42.1 32.3 35.1                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-9 B-6                                                              Feed [kg/h] 38.2 30.8 30.8                                                    in Section No. 5 5 5                                                          Further polymer C                                                             Type C-5 C-8 C-8                                                              Feed [kg/h] 31.8 46.2 46.2                                                    in Section No. 9 9 9                                                          Feed by.sup.3) SE SE SE                                                       Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 6-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 3.5 = 33% 4.4 = 54% 3.2 = 36%                   Rubber discharge [kg/h].sup.2) 0.1 = <1% 0.5 = 2%  0.3 = 1%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 7.0 = 67% 3.7 = 46% 5.6 = 64%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1 0.1 <0.1                                      [% by weight]                                                               ______________________________________                                        Example        VI-7       VI-8     VI-9                                       ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [Gew.-%]* 25 25 25                                              Feed [kg/h]** 42.1 42.1 42.1                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-9 B-9 B-6                                                              Feed [kg/h] 50 30.8 30.8                                                      in Section No. 5 5 5                                                          Further polymer C                                                             Type C-9 C-8 C-8                                                              Feed [kg/h] 50 46.2 46.2                                                      in Section No. 9 9 9                                                          Feed by.sup.3) SE SE SE                                                       Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 300 300 300                                                       Temperature in Sections 6-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 5.3 = 50% 5.9 = 56% 4.2 = 40%                   Rubber discharge [kg/h].sup.2) 1.6 = 4%  1.7 = 4%  1.1 = 3%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 5.2 = 49% 4.6 = 43% 6.3 = 60%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.2 0.2 0.2                                        [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) SE Side extruder                                                 

                  TABLE 7                                                         ______________________________________                                        Extruder configuration VII                                                    ______________________________________                                        Example        VII-1      VII-2    VII-3                                      ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [Gew.-%]* 30 30 30                                              Feed [kg/h]** 34.6 34.6 34.6                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-6 B-6                                                              Feed [kg/h] 76.3 76.3 76.3                                                    in Section No. 4 4 4                                                          Further polymer C                                                             Type --  --  --                                                               Feed [kg/h]                                                                   in Section No.                                                                Feed by                                                                       Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by                                                                       Extruder (main extruder):                                                     Speed [rpm] 260 240 220                                                       Temperature in Sections 4-12 240 240 240                                      [° C.]                                                                 1st squeeze section                                                           Water discharge [kg/h].sup.1) 4.9 = 47% 4.9 = 47% 5.1 = 49%                   Rubber discharge [kg/h].sup.2) 0.6 = 2%  0.5 = 1%  0.6 = 2%                   2nd squeeze section                                                           Water discharge [kg/h].sup.1) 0 0 0                                           Rubber discharge [kg/h].sup.2) 0 0 0                                          Devolatilization sections 5.5 = 52% 5.5 = 52% 5.2 = 51%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.1 0.1 0.1                                        [% by weight]                                                               ______________________________________                                        Example        VII-4      VII-5    VII-6                                      ______________________________________                                          Elastomer component A                                                         Type A-3 A-3 A-3                                                              Water content [Gew.-%]* 30 30 30                                              Feed [kg/h]** 34.6 34.6 34.6                                                  in Section No. 1 1 1                                                          Thermoplastic polymer B                                                       Type B-6 B-6 B-6                                                              Feed [kg/h] 71.3 76.3 71.3                                                    in Section No. 4 4 4                                                          Further polymer C                                                             Type C-6 --  C-6                                                              Feed [kg/h] 5  5                                                              in Section No. 1  1                                                           Feed by.sup.3) GD  GD                                                         Additives D                                                                   Type -- -- --                                                                 Feed [kg/h]                                                                   in Section No.                                                                Feed by.sup.3)                                                                Extruder (main extruder):                                                     Speed [rpm] 220 300 300                                                       Temperature in Sections 4-12 240 240 240                                      [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 4.1 = 39% 4.2 = 40% 5.0 = 48%                   Rubber discharge [kg/h].sup.2) 0.5 = 1%  0.5 = 1%  0.6 = 2%                   Devolatilization sections 6.3 = 61% 6.2 = 60% 5.3 = 51%                       Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content 0.1 0.1% 0.1%                                      [% by weight]                                                               ______________________________________                                        Example            VII-7                                                      ______________________________________                                          Elastomer component A                                                         Type A-3                                                                      Water content [Gew.-%]* 30                                                    Feed [kg/h]** 34.6                                                            in Section No. 1                                                              Thermoplastic polymer B                                                       Type B-6                                                                      Feed [kg/h] 76.3                                                              in Section No. 4                                                              Further polymer C                                                             Type                                                                          Feed [kg/h] --                                                                in Section No.                                                                Feed by                                                                       Additives D                                                                   Type --                                                                       Feed [kg/h]                                                                   in Section No.                                                                Feed by                                                                       Extruder (main extruder):                                                     Speed [rpm] 280                                                               Temperature in Sections 4-12 240                                              [° C.]                                                                 Squeeze section                                                               Water discharge [kg/h].sup.1) 3.7 = 36%                                       Rubber discharge [kg/h].sup.2) 0.4 = 1%                                       Devolatilization sections 6.6 = 63%                                           Steam discharge [kg/h].sup.1)                                                 Extrudate moisture content <0.1                                               [% by weight]                                                               ______________________________________                                         .sup.1) Percentages based on line * = 100                                     .sup.2) Percentages based on line ** = 100                                    .sup.3) GD Addition of granules                                          

The 46 Examples demonstrate the versatility of the novel process. Fivedifferent elastomer components A, eight different thermoplastic polymersB, seven different further polymers C and eight different additives Dwere used in a very wide range of combinations, with the result thattoughened thermoplastics or polymer blends of very different types wereprepared.

In the Examples, from 26 (Example II-2) to 74% by weight (Example III-5,the sum of both squeeze sections) of the residual water initiallycontained in the partially dewatered rubber were removed as liquid waterin the squeeze sections. The arithmetic mean over all 46 Examples of theresidual water removed in the squeeze sections was 46% by weight. Theremainder to 100% by weight was removed as steam in the devolatilizationsections (apart from the small extrudate moisture content). Thedifferences between the percentages for the sum of discharge ofsqueezed-out water plus steam discharge and 100% by weight are duepredominantly to rounding inaccuracies.

The rubber discharge is small, being on average about 2% by weight andnot more than about 5% by weight of the amount of moist rubber (ExampleV-1).

The Examples demonstrate the flexibility of the process even with regardto the throughput. The flow rates of the individual components could bevaried within a wide range:

elastomer component A: from 25.0 kg/h (Ex. II-6) to 159.1 kg/h (Ex.V-1),

thermoplastic polymer B: from 10 kg (Ex. III-4) to 124.2 kg/h (Ex. V-1and V-2),

further polymer C: from 5 kg/h (Ex. VII-4 and VII-6) to 60 kg/h (Ex.IV-6),

additives D: from 0.5 kg/h (Ex. III-7) to 8 kg/h (Ex. II-4).

In particular, it was possible to prepare both products having a lowelastomer content and products having a high elastomer content.

The individual components could be fed to the extruder in differentsections: in the Examples,

component B was introduced into Section 4 (Ex. VII), into Section 5 (Ex.I, II, IV, V and VI) or into Section 6 (Ex. III);

component C was introduced into Section 1 (Ex. III-4, VII-4 and VII-6),into Section 9 (Ex. II-4, II-6 to II-9, IV-2 to IV-6, VI-2 to VI-9 orinto Section 10 (Ex. III-1, III-5 to III-7, III-9 and III-10);

component D was introduced into Section 1 (Ex. I-2, I-3, II-7 andIII-3), into Section 9 (Ex. II-1 to II-4, II-8 and II-9), into Section10 (Ex. II-5, III-6 and III-9), into Section 11 (Ex. III-7) or intoSections 10 and 11 (Ex. III-2, III-8 and III-10).

The location of the feed was accordingly also variable.

Extruders with different screw diameters (40 mm and 58 mm) were used forthe process. The rate of rotation of the screw was likewise varied, andwas set at from 300 to 220 rpm in the examples: 300 rpm, 285 rpm (EX.V), from 220 to 300 rpm (Ex. VII).

It was also possible without difficulty to operate the extruder with a"dry" second squeeze section (no water discharge) (Ex. IV, VI and VII).

It was possible to operate the extruder in a trouble-free manner in eachof its seven configurations over a long time, trouble-free extruderrunning times of several hundred hours with varying products beingachieved.

We claim:
 1. A process for the preparation of toughened thermoplasticsor polymer blends containing toughened thermoplastics, thethermoplastics or the polymer blends comprisingA) from 5 to 95% byweight of at least one water-moist elastomer component A containing upto 60% by weight of residual water, B) from 5 to 95% by weight of atleast one thermoplastic polymer B, C) from 0 to 95% by weight of atleast one further polymer C, and D) from 0 to 70% by weight of additivesD,by mixing the elastomer component A with the thermoplastic polymer Band, if present, the further polymer C and, if present, the additives Din an extruder with mechanical dewatering of the elastomer component A,wherein the components A, B, C and D are fed to an extruder which has atleast two screws rotating in the same direction or in oppositedirections and having a screw diameter D_(Screw), and, in the conveyingdirection, the extruder being essentially composed ofat least onemetering section into which elastomer component A is fed to the extruderby a metering device, at least one squeeze section which serves fordewatering the elastomer component A and contains at least a firstretarding element and at least one dewatering orifice which is presentupstream of the first retarding element by a distance corresponding toat least one screw diameter D_(Screw), at least one feed section inwhich the thermoplastic polymer B is introduced as a melt into theextruder, at least one plastication section provided with mixing orkneading elements, at least a last devolatilization section which isprovided with at least one devolatilization orifice and in which theremaining water is removed as steam, and a discharge zone, wherein someor all of the water emerging from the dewatering orifices is present inthe liquid phase, wherein the components C and/or D are fed to theextruder together or separately from one another, either together withthe components A and/or B or separately from A and B and wherein thescrews of the extruder have a flight depth ratio D_(Screw), external/D_(Screw), internal of from 1.2 to 1.8.
 2. A process as claimed inclaim 1, wherein the extruder is a twin-screw extruder having screwsrotating in the same direction.
 3. A process as claimed in claim 1,wherein the extruder has, between the last devolatilization section andthe discharge zone, a further section in which the components C and/or Dare fed to the extruder together or separately from one another by atleast one metering device, and wherein this further section is providedwith mixing and/or kneading elements.
 4. A process as claimed in claim3, wherein the metering device for the component C and/or D is anextruder.
 5. A process as claimed in claim 1, wherein the discharge zoneis terminated by a die head and a melt filtration apparatus present,when viewed in the conveying direction, before the die head.
 6. Aprocess as claimed in claim 5, wherein an apparatus for melt granulationis present behind the die head.
 7. A process as claimed in claim 6,wherein the apparatus for melt granulation is operated under water.
 8. Aprocess as claimed in claim 1, wherein no Seiher housings are used asdewatering orifices in the squeeze sections.
 9. A process as claimed inclaim 1, wherein the extruder is not heated in the metering sections forthe elastomer component A, and wherein the extruder is not heated in thesqueeze sections.
 10. A process as claimed in claim 1, wherein theextruder has, downstream in the region behind the feed section for themelt of the thermoplastic polymer B and before the end of the extruder,at least one further feed section for the melt of the thermoplasticpolymer B.
 11. A process as claimed in claim 10, wherein the furtherfeed section for the melt of the thermoplastic polymer B is locatedbetween the last devolatilization section and the discharge zone, or inthe discharge zone.
 12. A process as claimed in claim 1, wherein, in thedevolatilization sections, the devolatilization orifices are arrangedlaterally on the extruder.
 13. A process as claimed in claim 1, whereinthe components C and/or D are fed to the extruder in a vent sectionlocated in the direction opposite the conveying direction of theextruder from the metering section.
 14. A process as claimed in claim 1,wherein the components C and/or D are fed to the extruder also in thesection in which the thermoplastic polymer B is introduced into theextruder.
 15. A process as claimed in claim 1, wherein the components Cand/or D are fed to the extruder also in the metering section.
 16. Aprocess as claimed in claim 1, wherein the screws of the twin-screwextruder are two-flighted.
 17. A process as claimed in claim 1, whereinthe components C and/or D are fed to the extruder in thedevolatilization section or in a further section which is locateddirectly before the discharge zone.
 18. A process as claimed in claim 1,wherein the extruder is operated at a screw speed of from 50 to 1200 rpmand mean shear rates, based on half the flight depth of the screw, offrom 15 to 450 s⁻¹.
 19. A process as claimed in claim 1, wherein atleast one graft rubber having a residual water content of up to 60% byweight is used as elastomer component A.
 20. A process as claimed inclaim 1, wherein a two-stage or multistage graft rubber containing abase stage comprising one or more of the monomers butadiene, styrene,alkylstyrene, alkyl acrylate, alkyl methacrylate and optionally smallamounts of crosslinking monomers, and a graft stage comprising styrene,alkylstyrene, acrylonitrile, methyl methacrylate or a mixture of thesemonomers is used as elastomer component A, and a styrene/acrylonitrilecopolymer, an α-methylstyrene/acrylonitrile copolymer, polystyrene,polymethyl methacrylate, polyvinyl chloride or a mixture of thesepolymers is used as the thermoplastic polymer B.
 21. A process asclaimed in claim 1, wherein a graft rubber based on polybutadiene orpolyalkyl acrylate as the base stage and a copolymer of styrene andacrylonitrile as the graft stage is used as elastomer component A, and astyrene/acrylonitrile copolymer is used as the thermoplastic polymer B.22. A process as claimed in claim 1, wherein a two-stage or multistagegraft rubber which essentially comprises polyalkyl acrylate and acopolymer of styrene and acrylonitrile is used as elastomer component A,and a styrene/acrylonitrile copolymer is used as thermoplastic polymerB.
 23. A process as claimed in claim 1, wherein the component Cisidentical to the component B but fed to the extruder at another pointthan the component B, or a thermoplastic polymer based on the monomersused for the preparation of the thermoplastic polymer B, having the sameoverall composition but with a different average molecular weight M_(w)or with other amounts of the monomers, or a polymer obtained bycopolymerization of C₂ -C₈ -alkenes with vinylaromatics, with polarcomonomers, with carbon monoxide, with nonaromatic vinyl compounds orwith basic monomers, or a polymer based on α-methylstyrene/acrylonitrileor methyl methacrylate/alkyl acrylate, or a polymer based on a rubbercomprising butadiene and, optionally, comonomers, or a polymer preparedby anionic polymerization of butadiene and styrene, in which optionallysome or all of the olefinic double bonds have been hydrogenated, or apolymer based on a thermoplastic polyurethane, or a polymer based onpolycarbonate, or a polymer based on styrene, acrylonitrile, methylmethacrylate, maleic anhydride and maleimides, or a mixture of at leasttwo of these polymers.
 24. A process as claimed in claim 19, wherein thegraft rubber is particulate and has graft rubber particles with adiameter of from 0.05 to 20 μm.
 25. A process as claimed in claim 24,wherein the graft rubber particles have a particle size distributionhaving one maximum (monomodal), two maxima (bimodal) or more than twomaxima.
 26. An extruder which has at least two screws rotating in thesame direction or in opposite directions and having a screw diameterD_(Screw), composed of the sections as claimed in claim
 1. 27. A processas claimed in claim 1, wherein an apparatus for melt granulation ispresent behind the discharge zone.
 28. A process as claimed in claim 27,wherein the apparatus for melt granulation is operated under water.